Previously, traces for each channel could not overlap, meaning that
channels would appear to artificially saturate. There are now two
parameters that determine the location of an LFP channel: plotHeight
and interplotDistance. Thus, plots can remain close together while
keeping a large range.

In order to improve rendering efficiency, the screenBuffer was changed
from a Juce AudioSampleBuffer to an array of GLfloats. Instead of specifying
each individual vertex, OpenGL receives a glVertexPointer. Exact timing
improvements have not been measured, but they should be significant.