plots the firing frequence as a function of time for all clusters of a sorted channel
SYNOPSIS
function plotInstFiringOfClusters( filename, clusters )
DESCRIPTION
plots the firing frequence as a function of time for all clusters of a sorted channel
used to check if there is electrode movement
urut/oct06
clusters={3298,2901};
load('/data/SF_032406/sortNORE/5/A8_sorted_new.mat');