Fixing 404 on page view when using PostgreSQL

closes #1801 
- adding fixBools method to `server/models/base.js` to convert bools to 1/0 to be consistent with MySQL & sqlite3 data providers (based on @ErisDS recommendation)
- this in turn fixes the check in `server/controllers/frontend.js`, which does an explicit `post.page === 0` comparison (in pgsql this is a `boolean`, since the schema declares it as "bool" in `server/data/schema.js`, but MySQL/sqlite3 don't have concept of Boolean, only an integer or bit)
- any model retrieved from persistence will pass through this (possible future refactoring is to combine fixBools & fixDates into one "canonicalize()" to have a single loop pass)