[#1079] Update path handling to only use backslashes.

Problem description
===================

Paver was dealing with native paths.
So on WIndows it was using "c:\test" ... but then if that was was written into a file
and then read again, the slashers were not excaped.


Changes description
===================

All paths are not handled using backslashed.

Also path conversion method was refactored into a single method.


How to try and test the changes
===============================

reviewers @alibotean 

Nothing special here.

I ran a test_remote all on server using this version and all looks ok.

You can try this version on your computer.