base: fix dangerous demosite populate

* NOTE `inveniomanage demosite populate` asks for user confirmation or
  `--yes-i-know` argument.  (closes #2294)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
oauth2server: addition of translatable strings

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
oauth2server: confidential and public clients

* Adds option to new application form to ask user for client type.
  (addresses #2113)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>