Ability to group several build definitions#12

Merged

jlandersen merged 5 commits intojlandersen:masterfrom michelkaporin:master

Jun 28, 2017

+135-65

Commits on Jun 15, 2017

Removed non-working command name, code tidy up.
michelkaporin
committed

Commits on Jun 16, 2017

Commits on Jun 20, 2017

Documentation update, added typing and grouped build def description change.
michelkaporin
committed

Commits on Jun 28, 2017

Handle empty active definitions list.
michelkaporin
committed