Add optional timestamp filters

Ensure that station columns exists before performing a query
Work with generators instead of lists

Fix some tests, some still do not work,
because of the generators
Improve tests for coincidence_queries

Add tets for new methods
Fix broken tests because of existing methods, using new methods, etc..
Merge branch 'coincidence_query_improvements'

Improvements to the coincidence_query module
Bump version to 0.9.12

Improved CoincidenceQuery to be more reliable.
Add timestamp filtering and ensure station columns exist
Speed up for ProcessEvents by using a generator for the trace.
Be smarter when looking for a trigger.