deposit: refactoring bug fixes

* Fixes several JavaScript issues introduced during refactoring of assets
  as well as dynamic field lists.

* Fixes tag template issue in field lists.

* Fixes issue when appending new elements to field lists.

* Fixes typo in message variable names.

* Fixes uninitialized variables due to strict mode.

* Removes Invenio CKEditor configuration as this is configured by each
  textarea field in the data-ckeditor-config attribute.

* Adds SPAN-tag to whitelist of HTML-tags to support MathJax integration
  in CKEditor.

* NOTE Changes deposit/form.js module to export multiple methods.
  If your instance templates invokes 'form(configuration)' it must
  be changed to 'form.init(configuration)'.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>