[Stephen Girard] Catalog query does not quote the db name on Snowflake

[drewbanin]

Issue

Issue description

Seen in the wild: dbt's catalog queries on (at least) Snowflake don't always quote relation parts correctly. Specifically, this was seen when generating the catalog for Sources. We've seen:

• quotes inside of quotes (where table_schema = '"schema"')
• missing quotes (where table_schema = schema)

TODO:

• Reproduce on Snowflake
• Determine if this can happen on other databases
• Add tests for different quoting configs across databases
• Make sure our documentation for how to supply source db/schema/identifier names is rock-solid

System information

The output of dbt --version:

0.13.0-a2