Implemented some enhancements to the form builder:
- support a -mode switch on forms, which can be either 'display' or 'edit'. If 'display', all fields are grayed out, and the pretty value is displayed instead of the internal value (e.g. the label of the element of a list).
- support multiple buttons on the form. Used for the 'Edit' button, but can be used for other buttons as well.
- Fixed all the standard templates to include the new buttons and to use the <label> tag.
- Added an example to the documentation showing how this new display/edit mode looks.
