Use new record type to handle repeated fields in view.

This is the first stage to generalizing the repeated field logic so that it can be
created and used for arbitrary foews (e.g. for BibEntry to use BibJSON-like structures)

Also:
Delete Field_uri and use existing Field_property.
Update FieldDescription to include repeat field and reference field group details.
New version of FieldDescription, and new RenderRepeatGroup renderer, with local tests.
Rename 'View_field' to 'View_field_view'
Update logging and code comments in preparaion for continued refactoring.  Reinstate SubGroupValueMap.
All tests pass.

Next step:
Refactor FieldDescription to allow use of dynamically provided field list (from list description)
Unify handling of repeated values across views and lists.
Refactor RepeatValuesMap to share code with FieldValueMap.
Moved form building utilities to sub-directory.
Clean up use of context data structures for repeated value rendering.
Allow EntityFinder to raise error if required view context information is missing.
Add entity type field to field description view
Rework bibliographic entry definitions to use repeat-field-group structures.
(Being able to generate BibJSON-like structures in the data is a chosen real-world
test case for the new repeat-field-group capability.)
Save changes prior to fiddling with CSS and list templates
Remove old repeating field logic from entity editing template.
Move list header generating logic from list template to RepeatGroup item renderer
Merge branch 'rework-form-mapper' into develop

This merges significant changes to the form generating logic into the main development branch.

The changes include simplification and rationalization of the field rendering logic, and
moving and unifying handling of repeated fieldc groups (used in entity and list views) to
be handled by a new field rendering module instead of logic in the edit/list templates.
These changes depend on a new capability introduced in Django V1.7.

Form generating support utilities have been moved to a separate subdirectory to make
them easier to locate and to ease maintanance.

Repeated field groups can now be defined through the interactive form definition
interface, with repeating field groups defined as a kind of view.

A new rendering option has been created for presenting repeated field groups in
an edit form as a table, and this has been used for the view editing form.
A revised BibEntry view uses the older style of grouping labeled fields over
one or more rows.

All 415 tests pass.
Fix up site data for BibEntry field selection; layout changes; update TODO.
All 415 tests pass.