allow enabling/disabling media components

[bill-auger]

allow enabling/disabling independently:

• screencap
• camera
• text
• interstitial
• audio
• output
• preview

[bill-auger]

• limited code support for this (mainly FAUX_*_SRC debug switches)
• camera bin is bypassed when no devices detected (c216647)
• interstitial may simply be an override over all other inputs
• GUI support is implemented (3d43b26)

[bill-auger]

ScreencapBin , CameraBin , AudioBin implemented
pending TextBin #22 , ImageBin #19

[bill-auger]

the ImageBin toggle operates mostly as intended (media override/fallback) except for audio

still pending TextBin but it should be trivial to adapt the switching functionality to accommodate this