Simple fixes for type warnings

Resolves: https://www.pivotaltracker.com/story/show/60810250

Using non-deprecated HTTP client machinery
Using non-deprecated HTTP multipart machinery
Simpler config for IT HTTP client
Basic add/delete property functionality
Basic add/delete property functionality
Adding custom predicate URI field, handling quoted or unquoted URIs and literals, suppressing deletion widget for JCR-managed properties
Merge branch 'editable-views' of github.com:futures/fcrepo4 into editable-views