Added filter metadata

Created list of all scalar filter options, by filter.
Created model for returning filters w/metadata

- Tests and implementation
Merge branch 'feature/46-filters-data' into feature/46

Ability to model filters for use with API.
Minor test fixes

- config had several bare strings, leading to test warnings
- test was referring to validators, and not filters
- implementation was resetting key, not value
Created factory for filters model
Created controller and factory for filters service

- Created controller
- Created corresponding factory
- Added model and controller factories to configuration
Created API service configration for filters

- Added routing, rest, and content-negotiation configuration.
Merge branch 'feature/46'

Implements new features for the input filter UI, including:

- Ability to create and manipulate filter chains for individual fields
- Ability to mark individual fields as required