[Feature development] A native oscilloscope plugin

[bratpeki]

Hello!

I am currently developing an oscilloscope for LMMS.

Initially, it is meant to be similar to the oscilloscope available at the top of the main window toolbar, except that it will be applicable to any effect stack.

Then, I would like to be able to change the time window window of the oscilloscope, so that it can be used a time-variable waveform display, which is useful for mixing.

Then, I would implement pitch detection capabilities, so the oscilloscope can keep periodic signals steady.

This issue has been made as per the statement made in the LMMS README: "Before coding a new big feature, please always file an issue..."

Please do keep in mind that, despite having contributed and written LMMS code before, this is my first time making a plugin. I would still like to develop it myself, with suggestions and help from interested and experienced developers, since the experience would make contributing in the future easier.

Thoughts?