Add an option/category in Dev Set to customize the device hostname (2/2).

PS2:
- cleanup

Change-Id: Iee14e90fa6fb6a13a123d92b7cf6dceaf6d18ffc
Port "Option to hide Adb notification icon (1/2)"

Frameworks part is already in place

Change-Id: Ie65625305153b45012846f6d2250fb707c4eebfd