Reordered examples/Makefile.am and added observer.py
Updated examples/README
Added get_stream_engine() again to call.py

call-gtk.py needs it and it was removed in commit 78e2d293d2888b90
Modified examples. Changes are:

Added #!/usr/bin/python to the beginning of each example.
Added usage() to those example which had not yet and were failing.
Documented what does each example do.
Changed to #!/usr/bin/python to  #!/usr/bin/env python
Given execution permissions to examples
patched minor syntax errors for python3.3