Filterfragmentfixes

[bitner]

Related Issue(s): #

Proposed Changes:

1. Fix examples in fragments/filter/README.md so that cql2-text examples are exactly equivalent to cql2-json examples. (This allows use within tests to make sure that a cql2-text parser returns the same AST as a cql2-json parser.)

PR Checklist:

• This PR is made against the dev branch (all proposed changes except releases should be against dev, not master).
• This PR has no breaking changes.
• This PR does not make any changes to the core spec in the stac-spec directory (these are included as a subtree and should be updated directly in radiantearth/stac-spec)
• I have added my changes to the CHANGELOG or a CHANGELOG entry is not required.

[bitner]

@philvarner I added some fixes to the examples so that the examples can be scraped and used to make sure that the pygeofilter cql2-text and cql2-json parsers have identical results.