split the obese sql.py into sql/*.py
added a few missing docstrings
base query classes moved from query/__init__.py into query/base.py
moved name factory aliases from query/__init__.py to sql/name.py
cleaned up some duplicate imports
sql.base.merge_sql free function refactored into sql.base.SQL.merge static method
renamed CaseExpression to CASE
pubic symbols in query/__init__.py and sql/__init__.py
import ordering
added missing import