Merge branch 'f-quotes-around-datetimes' into 'dev'

Fix quotes around datetimes

# Summary

This MR will fix #39, i.e., queries with quoted datetimes and add corresponding unit tests.  It will also improve error handling for ill-formatted datetimes in queries.

# Focus

- datetime rule was removed in `CQLParser.g4` 

# Test Environment

Use `f-quotes-around-datetimes` in caosdb-pyinttests