Fixed spike detector crash

This fixes a segfault that happened when no electrode was selected on a spike detector (e.g., with no electrodes added); getSelectedItemIndex returns -1 in this case, which was causing an array bounds segfault in drawElectrodeButtons.

Conflicts:
	Builds/VisualStudio2012/open-ephys.vcxproj
	Builds/VisualStudio2012/open-ephys.vcxproj.filters
	Source/Processors/DataThreads/FPGAThread.cpp
	Source/Processors/ProcessorGraph.cpp

updated the project build configs to include the SpikePlot.cpp and .h files and exclude the previous plotters

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}

Modified the pngs for the 5th radio button to have a non-edge style.  Additionally I added a 6th button for generating spikes that has a spike waveform.  I don't have the Jucer running locally so I can't add these files to the BinaryData class.

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.