Sql view params

[iboates]

Howdy howdy and happy Friday

I needed expanded functionality for specifying parameters in published SQL View layers, so I have implemented it into the publish_featurestore_sqlview method.

Specific things to note:

• New optional parameter parameters, which is an iterable of dicts with names that correspond (snake_case to camelCase) to the necessary XML entries used by Geoserver to define the parameters for SQL Views (docs)
• Totally reworked TestFeatures to account for these changes, and made it automatically build up the necessary database and geoserver content, and tearing it down at the end.
• To the above point, I also expanded the stuff in tests/common.py to allow you to specify a database in which to run tests. Maybe some of the current "local only" tests can be refactored to use this as well.
• Two new dev dependencies were introduced, I hope that that isn't a problem. They are sqlalchemy and psycopg2, used to work with the database when setting up & tearing down the database during testing.

Let me know what you think, I can tweak this further

[iboates]

😱 I completely missed this PR!

#144

Sorry about that..

[iamtekson]

The PR looks good to me. Thank you for the valuable contribution @iboates.