[IDE] #3777, #3846, #3888, #3889 - Various fixes and improvements for the Form and Code editors

[StanZGenchev]

What does this PR do?

Adds primitive support for Velocity template file highlighting in the main editor. Adds a new category in the Form editor called "Display". It will contain controls which are not form inputs but could be included in the form to display information. Adds an image control to the Form editor. Adds support for static data in the select control in the Form editor. Adds support for dynamic data in the radio control in the Form editor. Adds a regenerate button in the Form editor.

What issues does this PR fix or reference?

#3777 #3846 #3888 #3889