Add basic logging

[SergioLuis]

It would be nice to have logging - even some basic one.
I have not looked thoroughly into this, so I can't apport much more. Investigate if we can use Visual Studio Code logging infrastructure, and create -if needed- a wrapper static class to use it with ease.

[mig42]

Probably the best option for this is to use the OutputChannel and write there all information we need. That's what other extensions seem to do.

For regular commands (update, checkin, etc.) we're not printing neither the cm path nor the command output.

For info commands (the two cm version and cm location that run when starting a shell) we're not printing neither the current directory, nor the cm path, nor the actual command and arguments.