swc-windows-installer.py: Rework install paths to use ~/.swc

swc-windows-installer.py: Rework install paths to use ~/.swc

Instead of cluttering the user's home directory with multiple
SWC-installed directories, reduce clutter and improve namespacing by
dumping everything inside ~/.swc.  Think of it as a SWC-specific
~/.local.  We avoid actually using ~/.local because users might
already be using that for other purposes.

Use os.makedirs to create the nano install directory if it does not
already exist, because ZipFile.extract uses os.mkdir internally, and
mkdir will not recursively create directories.