FORGE-903 Refactored RestFacet installation.

The installation can now triggered via the 'rest setup' command or the RequiresFacet(RestFacet.class) instruction on a Facet/Plugin.

Cyclic dependencies among the various Rest facets have been removed. Clients are now expected to declare a dependency on the RestFacet instead of the RestWebXmlFacet or the RestApplicationFacet classes.