bug 2874 [1/3]: schema changes for overriding blocked renewals

bug 2874 [1/3]: schema changes for overriding blocked renewals

Two new subpermissions of circulate were added:
- circulate_remaining_permissions
- override_renewals

Also, the following schema alterations were made
- permissions.code      : varchar(30) => varchar(64)
- user_permissions.code : varchar(30) => varchar(64)

  (The reason for this was because "circulate_remaining_permissions"
   was greater than 30 characters long and wouldn't fit.)

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>