skytools v3.7.1

Fixes:

• quoting: drop obsolete keywords from quote_ident
• quoting: add COL_NAME_KEYWORDs into quote_ident list
• querybuilder: use dbdict more consistently

Cleanups:

• basetypes: tune Protocol classes
• tests: avoid 'pointless-statement'
• sqltools: annotate dbdict
• checker: use 'with' with files
• modules: add .pyi annotations