Add global search

[GDay]

This will allow admin/managers to do a search over multiple models on any page they are. It's nothing fancy, it just searches the "name" of an item or the "first_name"/"last_name" of a user.

Lookups could be done through more complex vectors, but for now this should be sufficient. Using something more complicated would also make the lookups a lot harder as the models used to look through are not the same.

I am aware of packages like haystack, but I am refraining from using those right now as it would add a lot of bloat and extra dependencies to the project.

[coveralls]

coverage: 93.835% (-0.006%) from 93.841% when pulling 5bc6ecc73ef7e1d7d98faa131022749fc60b4ebb on add-global-search into a6f2f9a790c2b507b14cf9aa45a1a307bdc88b41 on master.