add python setuptools support

- add setup.py script,
 - switch to use images via "share:" resource name
   (this allows to work both versions of application:
     - system wide installation,
     - directly from source),
 - add .desktop file,
 - rename FlatCAM.py to flatcam and install it as an
   executable script.

make_win32.py

@@ -43,7 +43,7 @@ if sys.platform == "win32":
 buildOptions = dict(
     compressed=False,
     include_files=include_files,
-    icon='share/flatcam_icon48.ico',
+    icon='share:flatcam_icon48.ico',
     # excludes=['PyQt4', 'tk', 'tcl']
     excludes=['scipy.lib.lapack.flapack.pyd',
               'scipy.lib.blas.fblas.pyd',