GEnum nicknames can be used to set properties in JSON
definitions, so added a callout to the JSON example explaining
this, and showing how to derive the nickname for an enumeration
value.
Modified the example code to use nicknames as well.
There was too much in the example code to cover in a single
recipe, so I trimmed it down to demonstrate simple
UI building (no constraints, effects, animations, or signals).
Added a simple script and program to load it, to support
recipe on ClutterScript for UI definitions.
Also amended the Makefile (following the pattern of
the tests/interactive Makefile) to enable signal
connection from ClutterScript by passing -export-dynamic
to linker.
