Handle 'bundle' protocol in Resources.isDirectory. Fixes #3212

Within an OSGi container, URLs' protocol is "bundle://".

In order to detect if a resource is a directory, this fix
rely on the class loader's behavior, which differ between
the standalone JVM and within an OSGi environment.
Most notably, ClassLoader.getResource returns differently
when the resource's name end with a slash.

In a standard JVM, getResource doesn't care of ending slashes,
and return the URL of any existing resources. In an OSGi container
(tested with Apache Felix), ending slashe refers to a directory
(return null otherwise).

In order to test Resources.isDirectory when the protocol is "bundle://",
there are 2 options:
a) run the test within an OSGi container (using Pax Exam),
b) simulate the behavior of an OSGi class loader, which is the
implemented solution.
Update doc test source directories

The documentation tests have missed most sources
since being moved to the `working` directory.

Also update the few broken tests since this change.
Merge pull request #3414 from pvlugter/doc-tests

Update doc test source directories
Merge pull request #3406 from jlc/resources-in-osgi-bundle

Handle 'bundle' protocol in Resources.isDirectory. Fixes #3212