Fix for Bug 4991, Overhaul of Calendar interface

Fix for Bug 4991, Overhaul of Calendar interface

- Put hints, key, and existing holidays into right column
- Style entry form for added clarity and consistency with other
  forms in Koha
- Change the way dynamically displayed hints are shown to better
  match existing static hints in Koha's interface
- Add branch name (instead of branch code) for clarity
- Add the ability to add and edit holiday titles (previously
  only description could be edited).
- Add links to the list of existing single-day holidays and
  exceptions which opens the calendar to that month/year

Signed-off-by: Galen Charlton <gmcharlt@gmail.com>