USB working with MAVlink Parser.

Now everthing must be moved to the receiver service, and have a good clean up.
USB now in MAVlink service.

But this breaks the TCP connection.
Creation of a MAVlink connection class.

This way it's simple to add a new comunication object like Bluetooth. USB and TCP modules moved and tested.
But this breaks all the service logic (like onConnect and onDisconnect).
Movving settings menu option to super class.
Improving Mavlink Connection structure by using an interface.
Improving mavlink connecttion objects.

Now the connection is handled by the super class, and link specific functions by the child classes.
Preference option to chose between TCP and USB
Start the mavlink client whenever restaring the activity.

Like when comming from a preference screen.

This shoud fix #23 and fix #33.
Merge pull request #39 from arthurbenemann/issue6_USB

USB support
Closes #6