UX Improvements

[Informatic]

• Remember last selected input
• Show input state (undocumented public call: luna://com.webos.service.eim/getAllInputStatus, activate key is true on active inputs)
• Add support for back button (this now just opens home screen view, probably matter of adding "disableBackHistoryAPI": true to the manifest, or adding handling of back event...
• Add GIP support (autostart)
• Custom no signal display (current HDMI input state can be checked via private method luna://com.webos.service.tv.display/getHDMIInfo - probably need private call proxy in hbchannel service...)
• Broken settings button icon on 3.x