redefine uri:classloader: meaning to be the parent classloader of runtime.getJRubyClassLoader

this allows to set JRubyHome to uri:classloader:/META-INF/jruby.home for all situations where
there is a jruby.home packed inside a jar.

fixes problem with loadService and knoplerfish OSGi

fixed missed test and cleanup javadocs and add more junit-tests for uri:classloader:

make IsolatedScriptingContainer work on felix-4.2.1 and probably on other osgi frameworks outside the pax test cases
add testcase for the case where jruby.home is inside a jar but not on the context-classloader
Merge pull request #2278 from jruby/redefine-uri-classloader-meaning

Redefine uri classloader meaning