ALICE: update of `alice-external-resources.xml`

* (addresses #145) (addresses #517) (PR #552)
fixtures: new name "ALICE Learning Resources"

* (see PR #552)

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
testsuite: new file `alice-learning-resources.xml`

* (see PR #552)

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>