added parameters to allow plotting of the collimator signal
modified function which gets breakdown time
BIG FEATURE: Set breakdown time to be t=0 for all diagnostics.

* Introduced gen.set.breakdown.time.to.zero as an element in the
	diag_params dict.  This is set to true by default

* The breakdown time is determined by the tektronic hv data.
	np.diff is used to calculate a 'derivative' and see for the first
	element whose derivative passes a certain threshold.

* Smoothing is applied to the signal to help keep noise from fooling
	the threshold method.