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.

FlatCAM.py

@@ -1,32 +0,0 @@
-############################################################
-# FlatCAM: 2D Post-processing for Manufacturing            #
-# http://flatcam.org                                       #
-# Author: Juan Pablo Caram (c)                             #
-# Date: 2/5/2014                                           #
-# MIT Licence                                              #
-############################################################
-
-import sys
-from PyQt4 import QtGui
-from FlatCAMApp import App
-
-
-def debug_trace():
-    """
-    Set a tracepoint in the Python debugger that works with Qt
-    :return: None
-    """
-    from PyQt4.QtCore import pyqtRemoveInputHook
-    #from pdb import set_trace
-    pyqtRemoveInputHook()
-    #set_trace()
-
-debug_trace()
-
-# All X11 calling should be thread safe otherwise we have strange issues
-# QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_X11InitThreads)
-# NOTE: Never talk to the GUI from threads! This is why I commented the above.
-
-app = QtGui.QApplication(sys.argv)
-fc = App()
-sys.exit(app.exec_())