system.copy: refactor and enhancement

[wdavidw]

This action is using an old programming style. I hasn't been yet updated because it is quite complex. Once we get this done, there are a few functionnality we need to had. Here's the plan:

• #116 refactor current source code and validate all tests are ok
• #117 honors options uid, gid, mode or preserve current ownership and permission of the source file
• #118 introduce a glob option to copy all files match a glob expression (eg "/tmp/source/file-*.ext")