Bring all tools into one repository

[craftyjon]

Bring all required tools (firesim, firenode, firemix-audio-processor) into this repo and deprecate the separate repos. Reorganize the repo to make more sense; update README and Wiki; and try to improve the build process for the C++ projects.

[craftyjon]

Also, rebrand tools:

Firemix -> Firelight
Firesim -> Firelight Sim
Firenode, firemix-audio-processor: combine into one binary, add simple GUI, rebrand to Firelight I/O