Authenticate species endpoint if needed
Don't include the "udfs" dictionary

These fields are already included as "udf:XXX"
Disable automated unit scaling

Previously units were always scaled at compile time which led to code
like this:

t = Tree.objects.get(pk=1)
t.diameter = 1  # units set to "feet"
t.save()

t = Tree.objects.get(pk=1)
print t

>>> 12  # Unscaled and in "inches"

Now these transforms must be done explicitly with:
    convert_to_database_units and convert_to_display_units
Support a custom set of mobile api fields
Merge pull request #1129 from azavea/topic/misc-api-changes

Topic/misc api changes