updated the SignalGenerator to generate spikes of varying amplitudes and at a lower rate. Minor incremental changes were made to other files

changed the way that the SpikeDisplayCanvas lays out its children plots. It uses a more dynamic approach that allows plots of mixed types to be layed out in a (sort of) clean manner.

Also fixed various bugs

removed old plotting files (Tetrode, Stereotrode, Electrode) plots. They have all be replaced with SpikePlot.{h,cpp}

Signal Generator now generates fake action potentials!!! The phase dial can be used to scale up and down noise on the spikes

initial commit of SpikePlot.cpp and SpikePlot.h which define a general spike plotting object that can completely replace ElectrodePlot, TetrodePlot, StereotrodePlot. SpikePlot objects can be added to the canvas and render fine, however, eventually the Tetrode variant of the SpikePlot causes a segfault, probably due to the way that spikes are copied around in the SpikeDisplayCanvas.

Altered the default settings of SignalGeneratorEditor and SpikeDetectorEditor to reflect the desired values for debugging the spike viewers

fixed bug where the max size of a spikebuffer was 256 bytes, this is too small for tetrode spike, this value is not determined by a constant defined in SpikeObject.h

began porting code from stereotrode plot to tetrode plot. It shows up in the canvas and actually shows spikes after the display is panned or zoomed at least once. Although spikes only show up in 2 of the 3 waveform axes

fixed bug in SpikeDisplaCanvas that was preventing spikes from getting rendered. The variable samplePosition was created but not initialized. I set it to 0