azavea/OpenTreeMap-iOS — pull request #5 by ahinz (2013-01-25 15:42:40+00:00)
Title: Add in new filter type for choices-based lists

Previously we just had generic "Boolean" and "Range" filters.
This commit adds a new filter type:
OTMChoiceFilter

If the filter type is selected the dictionary should also
provide a "OTMChoiceFilterChoice" key with the name of the
choice field that they wish to filter filter on.

A complete filter definition looks something like this:
```xml
OTMFilterKeyKey
filter_pests
OTMFilterKeyName
Pests
OTMFilterKeyType
OTMChoiceFilter
OTMChoiceFilterChoice
pests
```