Raise a ReleaseVersionInvalid error if version does not satisfy model format

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>
Remove unused package and job rebasing code

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>
Validate format before validating presence

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>