BUG8446, Follow up: Improve local login fallback

BUG8446, Follow up: Improve local login fallback

- Local fallback was not very well implemented, this patch adds
  better handling for such cases allowing clearer failure messages
- This patch also adds the ability to use single sign on via the
  top bar menu in the bootstrap theme.

BUG8446, Follow up: Adds perldoc documentation

- Add some documentation to the Auth_with_Shibboleth module
  including some guidance as to configuration.

BUG8446, Follow up: Correct filenames to match guidlines

- Moved Auth_with_Shibboleth.pm to Auth_with_shibboleth.pm to match
  other files present on the system.

BUG8446, Follow up: Correct paths after file rename

BUG8446, Follow up: Implemented single sign out

- This follow up rebases the code against 3.16+ which managed to break
  some of the original logic.
- As a side effect of the rebasing, we've also implemented the single
  sign out element. Upon logout, koha will request that the shibboleth
  session is destroyed, and then clear the local koha session upon
  return to koha.  Due to the nature of shibboleth however, you will
  only truly be signed out of the IdP if they properly support Single
  Sign Out (which many do not). As a consequence, although you may
  appear to be logged out in koha, you might find that upon clicking
  'login' the IdP does NOT request your login details again, but instead
  logs you silently back into your koha session. This is NOT a koha bug,
  but a shibboleth implementation issue that is well known.

BUG8446, Follow up: Fixed bootstrap login via modal

- The bootstrap theme enable login from any opac page via modal. To
  enable this with shibboleth we had to make some template parameters
  globally accessible when shibboleth is enabled.

BUG8446, Follow up: Add template rules for Shibboleth and CAS

- Add template rules so that CAS and Shibboleth can coexist.

BUG8446, Follow up: Added default config to config file

BUG8446, Follow up: Embellished perldoc documentation

- Updated perldoc to correct detail about configuring shibboleth
  authentication.
- Updated perldoc to include subroutines and their respective functions.

BUG8446, Follow up: Enable configuration of match field

- Added clearer, more flexible, configuration of shibboleth attribute to
  koha borrower field matching for authentication
- Correcting of documentation to make it more clear to the current
  implementation
- Minor refactoring of code to reduce some code duplication

Signed-off-by: Matthias Meusburger <matthias.meusburger@biblibre.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>