This effect is based on the ftconv opcode example from the FLOSS manual.

I call this ftConvXtended because some extra effects are added to, well, the effect.

version 1.1, February 2018
- added warning when no or invalid impulse sound is used
- if no or incorrect impulse, then the effect is bypassed

version 1.0, September 2017
- latest GUI (Blue 2.7.0 or greater)
- equalizer with on/off switch
- high boost filter to compensate treble loss when convolving
- Early Reflection (ER), as well as the dry signal can be moved in time
- reverse option for the Impulse
- blur and blur2 option
- option to change the length of the Impulse
- option to skip some beginning of the Impulse