Sampling frequency of acquisition are sometimes hard-coded

[Timothysit]

In a few areas of the code - see here - the sampling frequency is hard-coded to 25000 Hz. Please update the code so that they are only determined by the user, as this may cause filtering issues when the user specifies a different sampling rate.

[Timothysit]

I have implemented the following changes

• dSampF from plotSpikeDetectionChecks.m is now user specified in the main script rather than hard-coded to be 25000, there is comment on MEApipeline.m to clarify that in most cases this should be equal to the sampling rate (commit 1e63ea556ee3e221d1f4c2f7459d8d2d7df50505)
• makeHeatMap.m now allows user to specify custom fs, but kept fs=25000 as default (I think this function isn't called in the main pipeline, so this is not critical, but just in case. commit: 50470e8)
• electrodeHeatMaps now uses Params.fs rather than hard-coding fs=25000 (commit: a4e2c75)
• detectSpikesNew.m now uses Params.fs rather than hard-coding fs=25000 when defining spike times (commit: 39eb94b)

Closing this for now until new issues directly related to sampling frequency specification are found.