Feature :: Greater flexibility for fields

### Major feature additions
  * Disable issue summary (subject) and details (initial message)
    * Tickets are created with the help topic as the subject
    * [ ] Tickets can be created without an initial message
    * [ ] Summary and message can be disabled per help topic
  * Fields are individually configurable for view, edit, and requirement rights, for both end-users and agents
    * Retires the "Allow client updates" option as it is now provided per field
       * [x] This option is cascaded to the individual fields on upgrade
  * Support requirement for ticket close, so tickets cannot be closed without data in one or more fields
    * Tickets with outstanding fields cannot be set to any status extending `closed`

### Screenshot Tour
![screen shot 2014-12-04 at 2 35 30 pm](https://cloud.githubusercontent.com/assets/672074/5305733/f62aa906-7bc3-11e4-8aac-0cbd622b0b58.png)
**Configure visibility and requirement settings for a field**

![screen shot 2014-12-04 at 2 36 48 pm](https://cloud.githubusercontent.com/assets/672074/5305741/0271393c-7bc4-11e4-86fc-11c1ad8f9331.png)
**Require some data before closing a ticket**

![screen shot 2014-12-04 at 2 39 10 pm](https://cloud.githubusercontent.com/assets/672074/5305754/2d68b638-7bc4-11e4-9abe-e98098147277.png)
**When editing a ticket, fields which require data for closing are highlighted**