Django 1.6 support (WIP)

Changes needed to move to Django 1.6, including:
* Update Python library versions in requirements.txt
* Changed {% url %} template tag syntax
* Removed simplejson, now using built-in json library
* Move to external localflavor library
* Cache program modules in ProgramModuleObj form instead of subclasses
* Changed test runner to mimic old Django behavior (see #954)
* Many regression bug fixes

Work in progress - see discussion of issue #618 and individual commits.