Limit which skills can be assigned to a character

A character can only be assigned a skill if that character belongs to a
campaign, and that skill's skillset belongs to the same campaign. Implement this
restriction via some metaprogramming black magic.
Update docstrings.

Update docstrings for two functions:
* `forms.generate_character_skill_form`
* `views._generate_formset`
added templates for hit location adding and viewing
also added the same for traits
Changed the body background color
fixed the post URLs in the skills, spells, and possessions update forms
also removed extraneous relic paragraph tag
Added URLs and docstrings for updating and viewing traits and hit locations
Merge remote-tracking branch 'origin/ui-improvements' into ui-improvements
added verbose names to a couple fields on the Hit Location model
these are the names that are displayed when the name is rendered
added table body tags around each form when formsets are rendered in templates
Added tables for rendering traits and hit locations
fixed the trait viewing page to actually say 'traits'
fixed the URLs for the trait and hit locations pages to actually point to the correct view.
Added views for traits and hit locations
Refactor Views
Merge remote-tracking branch 'origin/ui-improvements' into ui-improvements

Conflicts:
	apps/gurps_manager/views.py
Fixed a few things to make pylint happy
Added tests for the new views for hit locations and traits
Fix which paths forms are posted to.

Ensure that the `object/update-form/` paths only accept HTTP GET requests, and
`object/` paths accept both HTTP GET and HTTP POST requests.
Make code look cleaner.

Add comments and whitespace. Change tabbing on some lines of code, and perform
better error checking in some methods.
Move class methods to forms.py

Create the following functions in module `forms`:
* character_skill_formset
* character_spell_formset
* possession_formset
* trait_formset
* hit_location_formset

Also, in module `forms`, rename function `generate_character_skill_form` to
`character_skill_form`.

Make other changes as necessary to accomodate those changes.