Change Makefile app target to copy boss and deps in a rebar compliant fashion to project dir. No more path necessary.

This pull request is *incomplete* at this time, as it breaks windows support. I'm hoping @rambocoder could help updating the windows-make.bat script.

Also, the -n flag I use for cp and mv is not POSIX, although it is supported by Mac OS X and Ubuntu 12.04. (rsync would have been a better fit, but I reckon not all platforms have it installed by default)