Add prodversions and "prodcommit -f FILE"
The new 'prodversions' script, when run in a super-project, will print out the version of each submodule.
The 'prodcommit' script has been extended to take an optional '-f FILE' parameter, where FILE contains lines in the same format produced by 'prodversions'. It will check out each submodule with the commit reference given in the file before commiting the super-project.