First draft of new automatic versioning system

When you build CFBundleVersion and CFBundleShortVersionString will be
automatically generated.

CFBundleVersion will be the number of tags on the branch:
3

CFShortVersionString will be the last tag that you set:
1.0.6

Some extras added:

If you have untagged commits after the last tag this will be
appended:
1.0.6 (3)

If you have a dirty working state there will be a start appended:
1.0.6 (3) *