Add graphical user interface to signal-estimator

[gavv]

signal-estimator is a command-line tool for measuring latency and glitches over audio devices. It's not part of Roc, but it was developed with our needs in mind.

It would be very handy for debugging to have a graphical user interface, allowing to inspect input / output streams in real-time. It is suggested to develop such an UI using Qt + Qwt.

See further details here: https://github.com/gavv/signal-estimator/issues/6

UPD:

https://github.com/gavv/signal-estimator/issues/6 is finished, but there are more improvements to be done:

• https://github.com/gavv/signal-estimator/issues/17
• https://github.com/gavv/signal-estimator/issues/13
• https://github.com/gavv/signal-estimator/issues/14
• https://github.com/gavv/signal-estimator/issues/15
• https://github.com/gavv/signal-estimator/issues/16