Removal of old commands

[fluca1978]

With #289 merged, now commands like flush-all have been replaced by a new command line parsing syntax like flush all. Other commands have been changed, like config-set that is now conf set and so on.

So far, pgagroal-cli and pgagroal-admin will emit a warning when the user types an old command, and this is documented.

Sooner or later, we should remove the old commands from the command line.

I propose to keep the old commands at least for two minor releases, i.e., to remove them on 1.8 in order to let the users to switch to the new command line.

[jesperpedersen]

I agree with this

[fluca1978]

I am wondering if does make sense to let the application tell the user when a command will be removed.
So far, we have something like: config-set has been deprecated since version 1.6.
We could improve this with: config-set has been deprecated since version 1.6 and will be removed in version 1.8.

So, when we add another command that deprecates an old one, we could already explain to the user when this will be removed.

[jesperpedersen]

Nah, because we may go to 2.0 if I can find time for it...

Lets keep as is