Use relative imports for internal modules.
Overhaul query.search

- Require search config on query property query class instead of on
model.
- Support pagination using subquery join.
- Allow __simple_search__ and __advanced_search__ config to be lists if
__search_filters__ dict used.
Update docs with changes to query search.
Clean up test databases in teardown.
Update location change of QueryProperty.
Remove PEP8 exception mention and change default mkdocs port.
Fix Python2.6 and Python3 compatibility issues.
PEP8/PyLint
Clean up files after make test-full.