win32: _platform/win32: add support for win32

Angelos Evripiotisrequested to merge
aevri/platform_win32 into master

Copy the approach of 'Darwin' and provide a SandboxDummy.

This enables us to run 'bst workspace list' on Windows.

Requires !1623 (merged) in order to be able to run this far in the program.

Edited by Angelos Evripiotis

Merge request reports