Refactor database to implement inheritance better

[alexyuisingwu]

Refactor database to use better inheritance for comparisons/templates and corresponding attributes to reduce number of functions needed for similar functionality.

Upsides:

• quicker to add functionality common to child tables
• reduction in number of functions

Downsides:

• no way to know type or row without joining on all child tables (or storing additional information)
• removing from child table doesn't remove from parent without trigger
• hard to enforce disjoint (row should only belong to one child table)
• slightly increased storage (id's also stored in child tables)
• attributes may not all be in same table (spread across parent and child), so constraints may be more difficult

[alexyuisingwu]

Done