Bug 27858: Make Koha::Patron::Attribute->store raise an exception on invalid type...

Bug 27858: Make Koha::Patron::Attribute->store raise an exception on invalid type/code

This patch adds type validation to the ->store method. And exception
should be thrown if the type is invalid. Things currently explode in
such situations, so this doesn't change the behavior (just adding more
informative failure information).

To test:
1. Apply the previous patches
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Patron/Attribute.t
=> FAIL: No exception is thrown on the bad case, weird error
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass! Exception thrown!
5. Sign off :-D

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@helsinki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>