Add option to testing framework to dump all emails sent

Useful when using the testing framework to develop some part of Critic
where the contents of mails sent is of interest.
Add support for "pause, test, upgrade" loop in testing framework

When the --pause-upgrade-loop argument is used in conjunction with
one of the other --pause* arguments that makes testing pause, instead
of continuing the testing on ENTER, push HEAD in the local repository
to the tested system and upgrade it to that commit, staying paused.

A command to run locally before pushing HEAD can also be specified.
If this is something like "git commit -a -mWIP", this mechanism can be
rather convenient to use to quickly make changes and test them in an
installed system.