Improvements to resource admin

Used at Stanford Splash Spring 2013 scheduling weekend
Adds JSON module to all existing programs

Adds a South data migration to add the JSON Data Module to all existing
programs. The JSON Data Module is a dependency for many commonly-used
modules, so it is important that it be enabled for all programs.

The migration deletes all existing JSON ProgramModuleObjs, to avoid an
edge-case where duplicate JSON ProgramModuleObjs cause Django errors.
This is safe, because ProgramModuleObjs are automatically regenerated.
Always adds JSON module in new program setup

Adds some lines to the prepare_program setup function, to always include
the JSON Data Module in the list of selected modules. The JSON Data
Module is a dependency for many commonly-used modules, so it is
important that it be enabled for all programs.
Adds install() to add_json_module migration
Filters lunch from sections in scheduling checks
Fixes walk-ins bug in lottery

The lottery uses a ClassCategory's symbol attribute for certain logic,
including figuring out whether a class is a walk-in seminar or not.
However, the open_class_category's name (its category attribute) was
being passed to the template instead.

Fixes this by passing open_class_category to the template as a JSON
string, and referring to its symbol attribute when necessary.

In the future, it might be strictly better to do ClassCategory logic
based on id, rather than symbol, since it is possible for two
ClassCategory objects to have the same symbol (though we haven't run
into problems yet because we usually avoid this).

Used for Stanford Splash Spring 2013 lottery student registration.
Merge pull request #613 from learning-unlimited/resources_admin

Improvements to resource admin
Merge pull request #615 from learning-unlimited/scheduling_checks_fix

Filters lunch from sections in scheduling checks
Merge pull request #614 from learning-unlimited/enable_json_module

Enable json module
Merge pull request #616 from learning-unlimited/walkins-in-lottery

Fixes walk-ins bug in lottery
Merge branch 'stable-mar13' into main