new editor for patron attribute types

new editor for patron attribute types

Added new script under the Administration menu
to create, update, and delete patron attribute types.

Some things to note:

- once an attribute is created, its code cannot be changed
- the repeatibility and unique_id settings of an
  attribute type cannot be changed after creation -
  this is to avoid having to deal with changing
  constraints if an attribute type is already in use
  by patron records
- an attribute type cannot be deleted if it is
  used by any patron records
- this administration page is always displayed regardless
  of the value of the ExtendedPatronAttributes syspref.  If
  the syspref is off, the page will prompt the superlibrarian
  to turn it on if desired.

Signed-off-by: Joshua Ferraro <jmf@liblime.com>