FW-219. Add support for Visual Studio.

Now following the workflow: a new branch developer_FW-219 was created only with related changes.
I could not integrate VS13 into scons, so do the following for debugging in windows:

Run gnu target before compiling the project:
	scons board=python toolchain=gcc oos_openwsn

Open Visual studio project oos_openwsn.sln and build the project.