generic mustache generator

[stevebuik]

A new tab in the UI, next to downloads. Has a picklist at the top which is populated from a new custom meta-data type.

When user selects a "template" from the picklist, a mustache render is run using the "value" of that meta-data record and is passed both the diagram JSON and describes.

First e.g. is an Apex Builder class generator.

Also has a hidable long text area for developing new templates and seeing the re-render (debounced) on every change.