bug 2000: addition changes to rules editor

bug 2000: addition changes to rules editor

* Added ability to specify total loans allowed at a library
  for the default patron category.  If set, the default
  limit is applied if no rule for the specific library
  and patron category is set.
* Added ability to specify default total loans allowed
  for the default library; this is applied if no rule
  for the specify library is set.
* Form now indicates if the number of current checkouts
  allowed is unlimited.

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