Use token type in Parser instead of string comparisons

Minor memory leak

Reduce code duplication in Parser

comments and formatting

fix for #1265

Eliminate commit of empty batch in some tests

drop TableView isPersistent field

seems like it was a temporary thing while the CTE situation was being worked out

for consistency

it is redundant, we already have the isTemporary field in a superclass

Add INFORMATION_SCHEMA.COLUMNS.DATETIME_PRECISION

Preserve domain name in columns and add CASCADE | RESTRICT to DROP DOMAIN

Fix MySQL compatibility ALTER TABLE DROP INDEX with schema

misc tiny refactorings