Mustachio: Add property maps for each renderer class (#2434)

Mustachio: Add property maps for each renderer class

These property maps provide functions for each valid property of a given type.
Currently the maps only reveal how to get a value (for a variable node) and
resolve a bool (for a conditional section). Still needed are Iterable functions
and value functions, for repeated and value sections, respectively.

Author: srawlins