Generate a valid project by default

[stevendanna]

Omnibus was previously generating an invalid project by default
because it:

• Didn't include a version-manifest software definition
• Didn't include the "preparation" software definition
• Had an invalid Gemfile

This fixes those issues, getting us a bit closer to the Getting
Starting directions working out of the box for people.

Fixes #887
Partially addresses #841

Signed-off-by: Steven Danna [email protected]

Maintainers

Please ensure that you check for:

• If this change impacts git cache validity, it bumps the git cache
  serial number
• If this change impacts compatibility with omnibus-software, the
  corresponding change is reviewed and there is a release plan
• If this change impacts compatibility with the omnibus cookbook, the
  corresponding change is reviewed and there is a release plan

[tas50]

Thanks @stevendanna