Create fields from new instance API schema

The instance API has been updated to return all fields visible to the
current user and an array of field sections defining the explict
grouping and ordering of fields in the mobile apps.
Use more explict species field labels

The fields the tree detail table view now use the two-line "subheading"
style, so we have more room for detailed field labels.
Fix detection of a required numeric formatter
Add section titles

I elimitated the no-longer-used fieldSections property on the
Environment and replaced it an array of section titles parsed from the
instance API response.
Merge pull request #99 from jwalgran/topic/new-field-grouping

New field grouping