Add url suffix mapping support targeting JAXRS endpoints

For mapping normal HST requests towards an JAXRS endpoint an url suffix extension will be added.

By defining an suffix delimiter (default: "./") an incoming request path can be split between a "normal" HST request path and a suffix/remainder.
This suffix then can be used to map to an JAXRS endpoint.

When a suffix is detected, its split from the request path before sitemount/sitemap matching is done. The suffix itself is retained without the delimiter (so without leading '/'!)

The suffix mapping to JAXRS endpoint itself will need an "url-template" configuration allowing to redefine and extend the incoming suffix before dispatching as JAXRS request.
As the JAXRS endpoint definition is (for now) a compile time setting (annotation), there is no need nor use in making this configurable through the repository.
More appropriately, this "url-template" (better: JAXRS endpoint prefix) is to be defined/configured on the specific JAXRS invocating pipeline valve, hence configured through the Spring configuration. This will be dealt with in a different issue, not here.

The above logic and configuration will be needed for both (HST 2.10.+) sitemount (services) only and sitemap based matching.
Both ResolvedSiteMount and ResolvedSiteMapItem will provide a new API method: getPathSuffix()
And the HstRequestContext will provide a getPathSuffix() method too, delegating to ResolvedSiteMapItem or else ResolvedSiteMount if ResolvedSiteMapItem is undefined.