Use Liberty repository to install features.

If a server directory or packaged server is pushed, a user's server.xml will be included in the artifacts pushed to the cloud, and this will be used to configure the Liberty server. This code inspects the server.xml to determine the configured features and ensures that the features are available in the server used to run the user's application. This is done by donwloading any missing features (those not included in the Liberty Core edition) from the Liberty repository. This does not incldue user features (these should continue to be made available in the artifacts pushed).