config revisions, all tests passing

[MV10]

This PR is larger than I'd intended and I'm guessing it won't get reviewed, but perhaps the notes will generate some discussion/attention so I'll wait awhile before merging.

The primary goal was to simplify and improve consistency of configuration because:

• this is one of the most complicated sinks to configure
• use of the .NET DataColumn class and .NET System types was confusing and limiting
• inconsistencies mapping between SQL types and System types
• inconsistent type mapping behavior between .NET Framework and .NET Standard
• too much special-case code for Standard Columns as a side-effect of original implementation

High-level change list:

• complete rewrite of the docs to cover ALL features and types of config
• Standard and custom columns both use SqlColumn (name, size, type, etc)
• expanded DataType support to nearly all SQL column data types
• support for non-clustered indexing on nearly any column
• option to change table primary key
• option to use clustered columnstore indexing
• prepare .NET Framework XML config for full parity with JSON config (Unable to add LogType to ColumnOptions.Store from config appSettings #80, Configure various ColumnOptions via AppSettings. #119)

Unifying column representation (Standard Columns and custom columns) results in this PR touching most of the code base. It retains full backwards compatibility with existing config-by-code or external-config options, but it turned out to be pretty easy to address nearly every open feature request as a byproduct of what changed anyway.

Issues:

• fixes Support Clustered Columnstore Indexes (CCI) #68 support clustered columnstore indexes
• fixes Option to auto create index on ColumnOptions.AdditionalDataColumns #81 auto-create column indexes
• fixes Should autocreate schema when autoCreateSqlTable is true #107 auto-create schema if it does not exist
• fixes Add option to auto-create Properties column as DataType SqlXml  #130 support SQL's XML column data type
• fixes Enable user to control the column sizes #146 allow user to control column size
• fixes Use System.Data.SqlDbType enums for column types instead of .NET Types #155 use SqlDbType enums for column types
• fixes General config/SQL mismatches for custom columns #157 config/SQL mismatches for custom columns
• fixes Remove binary / varbinary support (reverse PR 117) #165 sink can't support binary/varbinary SQL types from PR Extend column definition in config #117

Although it adds new functionality, I argue this is actually a simplification because there are fewer arbitrary restrictions. Normal SQL types and features are simply available and working out-of-the-box now. There is less to know, less to learn, and less you can get wrong now.

Major features / changes:

• renamed CommonColumnOptions to SqlColumn (since it is now exposed)
• Standard Column subclasses override properties like DataType to restrict options
• AdditionalColumns (SqlColumn-based) replaces AdditionalDataColumns (DataColumn-based)
• AdditionalDataColumns deprecated with Obsolete attribute
• use of DataColumn class is now completely internal
• Standard Column Id.BigInt obsolete, set DataType = SqlDbType.BigInt instead
• internal DataColumns have ExtendedProperty ref to original SqlColumn
• table creation completely rewritten
• all SQL column data type handling works the same way everywhere now
• SelfLog warnings for use of deprecated features
• more throws for invalid option combinations, or SelfLog warnings if auto-corrected
• eliminated hard-coded Standard Column names, smarter ColumnName property
• ColumnOptions.PrimaryKey added (defaults to Id if included in Store collection)
• ColumnOptions.ClusteredColumnstoreIndex property added
• new unit tests, revised older tests for new SqlColumn support
• SQL column data type parsing now case-insensitive (including deprecated config)
• removed SQL binary/varbinary support, Serilog converts to truncated ScalarValue string
• eliminated several class files
• split ColumnOptions class into partial class files

Changes specific to .NET Standard configuration:

• Standard Column config has full SqlColumn support
• "id.bigInt" property deprecated, use "dataType":"bigInt"
• CCI via "clusteredColumnstoreIndex" property
• PK via "primaryKeyColumnName"

Changes specific to .NET Framework configuration:

• sync'd supported types with .NET Standard list
• internally config uses AdditionalColumns and SqlColumn instead of DataColumn
• moved all but the main config section class to the SQL sink namespace
• added central config method for new PR to expand appconfig support

[MV10]

Might be easiest to review the README rewrite:

https://github.com/serilog/serilog-sinks-mssqlserver/blob/eefaea2f84297727693c0508c02fa24375ea8d5f/README.md

[MV10]

Merging so I can PR the .NET Framework XML config changes...