Postgres backend requires quoting of identifiers

[lordpretzel]

This is due to a lack of backend specific analysis modules. The long term solution is to factor out common analysis code and then have backend specific analysis modules which override the standard implementation where needed. In the short term quoting all identifiers, e.g., "x" instead of x is a workaround. However, there are some minor bugs with how this is handled that need to be addressed:

• qualified attribute access converts to upper case, e.g., SELECT "r"."a" FROM "r"; would complain that "R" does not exist in the from clause.

[lordpretzel]

Quoting of identifiers is no longer necessary since identifiers are now handled in a backend-specific fashion