Bug 17492: Add a warning about age being of-limits and a button to update it

Bug 17492: Add a warning about age being of-limits and a button to update it

This patch adds a warning if a patron's age is out of limits if an assigned category.
It also adds a button allowing to change the category.

Test plan:
1) Apply patch
2) Create a patron and assign him a category having age limits set
3) Change patron's age to be older/younger than category's limits
4) At "Check out" and "Details" tabs you should see a warning with a
button allowing to change the category, eg.:
 - http://prntscr.com/cz7ch3
 - http://prntscr.com/cz7em4
 - http://prntscr.com/cz7dj1
5) Set a valid category according to patron's age
6) Warning should disappear
7) Perform similar test again, but instead of changing the age change
the limits of a category
8) During tests verify "Change category" button everytime opens "Modify
patron" page:
  http://prntscr.com/cz7g5q
9) Ensure that left-side panel is always on its expected place
10) Remove patron's date of birth and test that all categories are
allowed now
11) Run automated tests: prove t/db_dependent/Koha/Patron.t

Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>