Add helper script to perform online repository swap

E.g. if you have new version of the repository waiting
in pending area, this interacrive script can be used
to do the swap:

/pending/path/to/online/repo/tools_maintenance  ->
/path/to/online/repo/tools_maintenance

Backup of the existing/old repository will be taken
and placed next to new one.

Change-Id: Iadae85941a9522dbe28eb5decb8a562a5fab1dc2
Reviewed-by: Antti Kokko <antti.kokko@digia.com>