Add an option to change the device hostname

This adds an option to modify the device hostname used
in ip resolution. This is useful when connecting to the
android device in a dynamic dhcp environment.

The framework/base part is already present.

PS2: move preference above the debugging section

Change-Id: Ibc145b74036617248d4f33c6866cc9c8a8cc8974

Conflicts:
	res/values/strings.xml