[#368] Ported revision history page to new template system
[#408] Remove organizations (publisher) code
[#368] Refactor truncate in revisions table
[#368] Revisions table should not be condensed which would otherwise lead to display errors with in radio buttons
[#368] New templates for revisions
[#368] New template for revision diff
[#368] New template for revision read
[#368] New template for revision list
[#368] New template for group history
Merge remote-tracking branch 'okfn/master' into 368-new-history-page
[#368] Fix display of action buttons for revisions which broke after I merged in the latest master with new bootstrap.
[#368] Add `num_followers` after validating the group_dict against a schema.
This makes sure that is still there and is necessary because we require a schema in controllers.group.history but there is no `num_followers` field in logic.schema.default_group_schema.
[#368] Add `num_followers` to group schema
[#2750] Add example_idatasetform example extension
[#2750] Improve IDatasetForm docstrings

- Rewrite the IDatasetForm docstrings to make them clearer,
  and conform to PEP257
- Reorder methods in IDatasetForm and DefaultDatasetForm
  so that they're 1. in a more logical order and 2. in the
  same order as eachother
- Tell autodoc to put the methods in source-code order,
  not alphabetical, in the sphinx docs
- Remove docstrings from DefaultDatasetForm that are
  exact repeats of corresponding docstrings in IDatasetForm
- Add edit_template() to IDatasetForm, it was missing

db_to_form_schema_options() and form_to_db_schema_options() and some
other schema methods in DefaultDatasetForm are still missing from
IDatasetForm but I'm leaving it that way for now, consider them
unofficial.
[#2750] Delete 'Customizing Forms' docs

They are out of date, and we have ckanext/example_idatasetform instead
now.
[#471] Deprecate lib.helper link functions
[#471] Fix template for nav_named_link() removal
[#471] Fix template for subnav_link() removal
[#471] Use suggested function not direct link for clarity