bindings: python: examples: consistency cleanup

bindings: python: examples: consistency cleanup

A collection of minor changes to be more consistent with other examples:
 - capitalize comments
 - add line offset to value outputs
 - drop comma from edge event outputs
 - improve behaviour if run on a platform that does not match the
   example configuration
 - use with to cleanup request in toggle_line_value.py

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>