oauth2server: form field order
oauth2server: form field order

* Changes ordering of fields in client form.

* Adds extra documentation for public vs confidential clients.

Signed-off-by: Lars Holm Nielsen <7eaffca9f7cd98839b5821d0d23e09ff764b82cd@cern.ch>

inveniosoftware/invenio,tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio