fixes #6888 - remove duplicate presence validator causing two errors

fixes #6881 - check if in rake when validating template changes

fixes #6825 - refactor api/v2/filters_controller.rb to use find_optional_nested_object and add Authorizable to class Role

Fixes #6446 - Forbidding non-json POST/PUT requests in v2

Fixes #6566 - renaming a node now resets the certname on provision

If use_uuid_for_certificates is true, reuse the certname UUID value.
If false, then reset the certname if it does not match the hostname.

Fixes #813 - External usergroups can be linked to an LDAP auth source

Fixes #6786 - Handle error when no taxonomy params get sent

Basically, no organization params are getting sent as the bug reporter is not
using json and not using wrapped params. You can also test this by doing:

curl -X POST http://localhost:3000/api/v2/organizations...

Fixes #6816 - pass oVirt quota as nil instead of "" to prevent server error

Fixes #215: Parameters can be saved without a value

fixes #6636, #6657, #6694 - add field length validations, extend audit field length