Completely new config system, currently read-only.

Minimum pgsql version had to be bumped to 9.4 for
jsonb support. Existing json columns will probably
be changed to use jsonb in the future.

While the new config system cannot store values
yet (set() is unimplemented), you can still set
values manually in the database and purge the
cache for changes to take effect. The read-only
stuff is fully functional.

Date formatting in posts relied on subquerying the
the config table, which was retarded. Thus, all
dates will show up as the default format until I
can find a better solution.

Huge commit this time around. Sorry.