Devutils: wifi:activate

[pmartin]

First commands for devutils : to activate / deactivate wifi.

This means, on the code side:

• Adding a very crude parameter parsing
• Calling a different function for each existing command
• Not logging to graphical screen and exiting without waiting for a keypress when a known command has been run
• Splitting code to several files (a common header, one .cpp for each set of features + updated Makefile)

Two commands exist, for now :

devutils.app wifi:activate
devutils.app wifi:deactivate

The first one is already put to good use in app-receiver.app, BTW -- to ensure wifi is ON when trying to receive an application, even if it was previously in sleep mode.