Finish WIP3249 with proposed changes to WixStandardBA.
Merge pull request #15 from rseanhall/wip4161

WIP4161 - Allow more than one MBA prereq
Merge pull request #14 from rseanhall/wip3249

Finish WIP3249 with proposed changes to WixStandardBA.
Suggested improvements for WIP #4161.
Update WIP 3249.
Merge pull request #16 from robmen/master

Suggested improvements for WIP #4161.
Merge pull request #17 from rseanhall/wip3249

Update WIP 3249
Update WIP from wix-devs discussion.