Unset executable bit & remove !#shebang

Unset executable bit from all python sources upon installation, and
remove shebang from all python modules w/o `if __name__ == '__main__'`.

There are corresponding wrappers provided in the $(PREFIX)/bin/ for each
python script (not ui_*.py), so there should be no need to call these
source files directly as commands. Even those python sources which do
not have a script in $(PREFIX)/bin/ -- they are just being imported into
other modules, and their `__name__ == '__main__'` exists simply for
debugging purposes.

Also, restricting to only single valid entry point adheres to

  The Zen of Python
  =================
  There should be one-- and preferably only one --obvious way to do it.

Fixes #240

Makefile

@@ -159,7 +159,7 @@ install:
 	install -m 644 resources/scalable/claudia-launcher.svg $(DESTDIR)$(PREFIX)/share/icons/hicolor/scalable/apps/
 
 	# Install main code
-	install -m 755 src/*.py $(DESTDIR)$(PREFIX)/share/cadence/src/
+	install -m 644 src/*.py $(DESTDIR)$(PREFIX)/share/cadence/src/
 
 	# Install addtional stuff for Cadence
 	install -m 644 data/pulse2jack/*     $(DESTDIR)$(PREFIX)/share/cadence/pulse2jack/

src/canvaspreviewframe.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Custom Mini Canvas Preview, a custom Qt widget

src/claudia_database.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Package database

src/clickablelabel.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Clickable Label, a custom Qt widget

src/jacklib.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # JACK ctypes definitions for usage in python applications

src/jacklib_helpers.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Helper functions for extra jacklib functionality

src/patchcanvas.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # PatchBay Canvas engine using QGraphicsView/Scene

src/patchcanvas_theme.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # PatchBay Canvas Themes

src/shared.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Common/Shared code

src/shared_cadence.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Common/Shared code for Cadence

src/shared_canvasjack.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Common/Shared code related to Canvas and JACK

src/shared_settings.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Common/Shared code related to the Settings dialog