Support explicit schema selection for the migration table

[pnehrer]

Add the ability to specify a table schema for the refinery history table, in case a non-default schema is required:

• refinery cli takes an optional --table-schema argument
• when a schema is provided, refinery attempts to create it, if it doesn't exist, when asserting the existence of the history table
• all table operations subsequent to this use the qualified table name so that they are performed in the correct schema

[pnehrer]

@kriswuollett apologies in advance for my unfamiliarity with the process -- how can I get this PR reviewed? Thank you in advance!