Improve effect of caching in ChainedProperties.

The ChainedProperties utility has a caching setting that will cache the classpath discovery of property resource - but not the parsing of these resources.

This utility is a hot spot for the initialization of runtime environments - caching the parsed properties instead of the resource url will improve runtime performance.

Changing the caching strategy will make hot changes to classpath property resources impossible. File based property files could be made safe cacheable by investigating file metadata and only read if changed.