Refactor settings files

The current way settings work, they set a bunch of things and
then try to import local_settings.py, which means local_settings.py
cannot modify anything set in the importing file; it has to
completely override it.

These changes make local_settings.py the top-level file, which needs
to be created before anything will work. It should import any of a
number of environment-specific settings files (dev, staging, test,
production) and can then override anything it needs to.
DB settings in base; move local with others

* Add default database settings to pycon/settings/base.py
* Move local settings to pycon/settings/local.py
Require travel plans on financial aid form

More specifically, require travel plans on the financial aid
form if and only if a travel grant is requested. Implemented
by leaving the form field technically not required, adding
form validation that looks at whether a travel grant is requested,
and marking the travel plans field with 'required' styling
manually.
More translation updates

* Django settings to tell Django what languages we're using and where
  to find our translation files.
* Mark more strings for translation.
* Update the comments at the top of locale/fr/LC_MESSAGES/django.po
* Add some doc for how to translate
* Fix use of blocktrans in some templates
* Update finaid doc while I'm here
* Ran make_messages & compile_messages to update the translation files.
Limit speaker bio field to 100 words
No markdown for speaker bio; expand help text
Merge branch 'develop' into feature/78-refactor-settings
Merge pull request #172 from caktus/feature/translation-process-2

More translation updates
Merge pull request #171 from caktus/feature/171-limit-speaker-bios

Limit speaker bios to 100 words
Merge pull request #170 from caktus/feature/travel-plans-field

Require travel plans on financial aid form
Update settings to get server values from environment
Merge branch 'develop' into feature/78-refactor-settings
Adding selectable support to Add Speaker form
Address some PR feedback
resolve issues with clean and selectable, add validator to prevent adding the original Speaker author as a Speaker
Bool in env will be 'true' or 'false'
Mark more text for translation
Customize lookup get_query to account for looking up a portion of User.get_full_name
Merge pull request #174 from caktus/feature/translation-3

Mark more text for translation
resolve conflict from latest merge