Bug 16892: Add automatic patron registration via OAuth2 login

Bug 16892: Add automatic patron registration via OAuth2 login

10988 added the ability to log into the OPAC authenticating with
Google Open ID Connect. This extends it, by allowing an
unregistered patron to have an account automatically created
with default category code and branch.

This is accomplished by adding 3 system preferences.
- GoogleOpenIDConnectAutoRegister
      whether it will attempt to auto-register the patron.
- GoogleOpenIDConnectDefaultCategory
      This category code will be used to create Google OpenID Connect patrons.
- GoogleOpenIDConnectDefaultBranch'
      This branch code will be used to create Google OpenID Connect patrons.

Sponsored-by: Tulong Aklatan
Signed-off-by: Eugene Jose Espinoza <eugenegf@yahoo.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>