Install features from a private repository

[hughesj]

The LARS project provides a repository for hosting Liberty features. The Liberty installUtility command can make use of a privately hosted LARS repo by configuring a repositories.properties file. We're using featureManager which isn't able to use a LARS repo. So, this issue is to convert from using featureManager to using installUtility to install additional features.

• (the existing behaviour) ensure features can be installed from ibm.com without having to configure a repositories.properties file.
• install Liberty product features from a private repository
• install user features from a private repository