Enabling an easy version of the Clear-Host function

[sburnicki]

This has to be implemented differently once we support different hosts.
But for the sake of simplicity, I chose to implement it this way for now.

There is obviously no unit test as it's a UI-only thing with platform specific implementation, that we cannot test with out existing testing framework.
Fixes #382.

[JayBazuzi]

I'm glad that most of Pash is unit tested, but as you point out, no matter how vigilant we are, there will always be a handful of items that can't be tested that way.

What do you think of keeping a list, checked in to the repo? We can use it as a checklist/manual test plan before releasing, and as a TODO list of things to automate.

[sburnicki]

Yes, maybe that's a good attempt to keep track of these things.