doc : add stuff about UI in Python coding guide
doc : add stuff about UI in Python coding guide

Change-Id: Ib100c58733efa98b3da00b5fdded7e1e12659dc9
Reviewed-on: http://gerrit.aldebaran.lan:8080/64
Reviewed-by: Dimitri Merejkowsky <1e4b13000fa8777df4cefd2fd8215187e3deb062@aldebaran-robotics.com>
Tested-by: Dimitri Merejkowsky <1e4b13000fa8777df4cefd2fd8215187e3deb062@aldebaran-robotics.com>

aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild