Implement a CKAN plugin for database table creation

When writing a CKAN extension, new database tables are often required, which involves bypassing the toolkit and creating the models yourself, and installing them either with a paster command or at startup time during config.

It would be nicer if CKAN had a plugin that could be implemented and have the tables created by a ckan paster command (paster db install-plugins?).

Start by reviewing how CKAN extensions currently create database tables, including the toolkit, paster commands, and startup-time configuration described in the issue. Determine the plugin interface and command behavior needed for table creation, then define completion around a working CKAN paster command that installs tables for participating extensions.

Written by the indexing model from the issue text.