Videobox 2.6 - non-FOSDEM features

[gerryd]

Related to #264 but less useful for FOSDEM itself:

• Support for cheap-ish wired microphones
• Inline USB-powered XLR microphone preamp
• Support for an all-in-one setup (USB camera + slidesgrabber)
• Interface to start/stop recording
• Interface to start/stop streaming

[krokodilerian]

The video-box-mixer role takes care of the all-in-one-setup and it looks to work.