Add caqti-persist backend.
caqti-persist: Implement patch.
caqti-persist: Implement events.
caqti-persist: Add create function.
caqti-persist: Partial fix for empty nonpk.
caqti-persist: Add Insert_buffer, use it to fix create.
Support float and float(n) types.
Rename some nonterminals.
Accept various drop statements.
Fix nullable defaultable; change patch params; tweaks.
caqti-persist: Skip insert if pk has defaults.
Add test for caqti-persist.
caqti-persist: Improve merge semantics.
caqti-persist: Add Update_buffer and use it to fix update.
caqti-persist: Integrate events with cache; some fixes.
caqti-persist: Don't parenthesize RETURNING spec.
caqti-persist: Some adjustments to create and test case.
caqti-persist: Add getters.