docs/source:

Added risk docs to the table of contents. Previously, there were NO risk docs
at all.
calcs/risk/general:

Major docstring cleanup.
calcs/risk/hazard_getters:

Major docstring cleanup.
calcs/risk:

Major docstring cleanup (which removes a lot of warnings when building docs).
db/models:

Docstring cleanup.
calcs/hazard/classical/post_processing:

Docstring cleanup.
Merge pull request #1107 from larsbutler/clean-up-doc

Big docs cleanup

[r=matley]