If invoice is empty, move it for next month instead of confirming it.

Also add comments for each transition.

Check really only of registration invoice.

Previous local rebase -i by Cedric was buggy, leading to bad commits.

 - only_sr filter and force the run of a single SR, and uses url_md5 (folder_id)

 - only_cp filter which computer patition, will be runned. it can be a list,
           splited by comman (slappartX,slappartY ...)

Since 830e432a only email address is required.

Avoid creation of new software release state change packing list only if
similar one is the topmost one.

Cache for list is not implemented and in order to avoid hiding other problems
provide no cache variant of test.