Make sky_tool install to ios devices and simulators if available, and add a...

Make sky_tool install to ios devices and simulators if available, and add a ‘listen’ command that will listen to filesystem changes in the current directory and update running versions of the app.

Also refactors ios_sim.py to be part of sky_tool.

The current skyx file that ‘listen’ generates does not contain material design icons, so icons will be missing.