add sql-datasource; port datazilla sql datasource (with tests) to treeherder
added comments
fixed comments
fixed text
fixed comments
added primary key to option_collection
added request_ids reference to job_guid description
tests use cache versioning to keep isolation
remove cache.clear() from tests setup/teardown
remove unused import
remove old references to cron_batch
move webapp/models.py to model/models.py.
python-dev is required  to pip install MySQL-python
merge changes from master into sql-datasource
Merge pull request #12 from mozilla/sql-datasource

Add SqlDatasource to models
Merge branch 'master' into refdata-derived-models
add RefDataModel - not finished yet