NEXUS-7371: remove the automatic feature discovery in favour of a strict list of features to install

https://issues.sonatype.org/browse/NEXUS-7371
http://bamboo.s/browse/NX-OSSF405-1 :white_check_mark:

Still considering if it makes sense for the features list to be stored as a property or kept in its own file.
This is delightfully mysterious. :)