Add CLI commands for HDMI-CEC TV control (volume, power, input switching and some other controls)

[waydabber]

The following should be provided for CLI:

• get -CECReport to discover CEC capability and show some basic CEC technical info.
• perform -sendCEC=COMMAND -CECAddress=LOGICAL_ADDRESS to send various basic CEC commands (volume, mute, standby, wake etc) to the TV or alternatively if CECAddress is specified, other devices.

Related to: #3394

[waydabber]

Some examples:

Turn volume up by 1
betterdisplaycli perform -n=lg -sendcec=volumeup

Turn volume up by 5
betterdisplaycli perform -n=lg -sendcec=volume+5

Turn volume down by 3
betterdisplaycli perform -n=lg -sendcec=volume-5

Mute volume
betterdisplaycli perform -n=lg -sendcec=mute

Set TV to standby
betterdisplaycli perform -n=lg -sendcec=standby

Wake TV
betterdisplaycli perform -n=lg -sendcec=wake

Turn volume up by 5 on the AV receiver
betterdisplaycli perform -n=lg -sendcec=volume+5 -cecaddress=audiosystem

Commands available:
``volumeUp, volumeDown`, `mute`, `standby`, `wake`, `select`, `up`, `down`, `left`, `right`, `rootMenu`, `setupMenu`, `contentsMenu`, `exit`

Addresses available:
tv (0), recording1 (1), recording2 (2), tuner1 (3), playback1 (4), audioSystem (5), tuner2 (6), tuner3 (7), playback2 (8), recording3 (9), tuner4 (10), playback3 (11), reserved1 (12), reserved2 (13), freeUse (14), broadcast (15)

[waydabber]

Expanded the commands with input switching.

This should switch to HDMI 1 on many TVs (and so on...):
betterdisplaycli perform -n=lg -sendcec=input:1

This should switch to the input the Mac is currently connected to:
betterdisplaycli perform -n=lg -sendcec=input:mac