forms: Add concept of inline form fields

In-line forms are forms that are rendered as one field. The data of the inline form is also saved in the data for one field. Currently, the data is rendered to JSON and stashed in the database.

The data in the field is also accessible via the variable replacement system, so something line `%{ticket.field.subfield}` can be handled by the inline form field.

### Outstanding
  * [ ] In-Code documentation of new classes
  * [ ] PDF printing for inline fields

### Screenshot Tour

#### Form Edit
![screen shot 2014-05-26 at 09 07 48](https://cloud.githubusercontent.com/assets/672074/3083210/3656ab28-e4df-11e3-8696-0058e69bc139.png)

#### Field Configuration
![screen shot 2014-05-26 at 09 08 00](https://cloud.githubusercontent.com/assets/672074/3083209/31245934-e4df-11e3-8217-0d1bfec755b7.png)

#### Display for Agents
![screen shot 2014-05-26 at 09 07 32](https://cloud.githubusercontent.com/assets/672074/3083211/3a842a4a-e4df-11e3-85e4-04019ec28ff2.png)

#### Edit for Agents
![screen shot 2014-05-26 at 09 06 37](https://cloud.githubusercontent.com/assets/672074/3083196/07159a4a-e4df-11e3-9f32-6306c6d93253.png)

#### Display for Clients
![screen shot 2014-05-26 at 09 12 04](https://cloud.githubusercontent.com/assets/672074/3083249/f65e27e8-e4df-11e3-83da-2e71bbe9e933.png)

#### Edit for Clients
![screen shot 2014-05-26 at 09 13 07](https://cloud.githubusercontent.com/assets/672074/3083251/0170acbe-e4e0-11e3-93fa-fd1a32d5d42c.png)