[Hardy-netbook-lpia] SRU: Some modifications to the helper scripts

[Stefan Bader]

This is only for the netbook-lpia branch in Hardy and only affects the
scripts used to rebase the tree.
So no impact on the builds. This is more to document the changes. Those add
insert-ubuntu-changes for it, remove retag-branch (because its not needed)
and adds some checks and hints to rebase-branch.

-Stefan