support a flag to disable typeahead suggestions

[heswell]

There may be reasons to want to disallow typeahead suggestions on filter controls.
suggested steps

• update ServerAPI to add getTypeaheadSuggestions as an API method (right now it is a particular type of RPC request invoked via the rpcCall API method.
• update useTypeaheadSuggestions to use the new method
• allow a disableTypeaheadSuggestions flag to be passed into VuuDataSourceProvider and LocalDataSourceProvider, This flag would have to be propagated to COnnectionManager and provider of local ServerAPI, such that calls to getTypeaheadSuggestions could be handled with tha tflag available