Solved several issues with echo effects
Added overdrive effect
Added audio for testing purpose
Added sound.h for basic types
Added project description in /extra/doc
Renamed /src/echo to /src/fir_echo
Renamed /src/echo2 to /src/iir_echo
Modified WAVE files usied for testing purpose
Moved effects 101 info to /doc/effects
Commit math (work in progress)
Commit waveform (work in progress)
Commit wah (work in progress)