regtest for fourier transform

regtest/analysis/rt-fftw/Makefile

+include ../../scripts/test.make

regtest/analysis/rt-fftw/config

+type=driver
+plumed_needs="fftw"
+# this is to test a different name
+arg="--plumed plumed.dat --ixyz trajectory.xyz"

regtest/analysis/rt-fftw/plumed.dat

+c1: COORDINATIONNUMBER SPECIESA=1-10 SPECIESB=11-20 SWITCH={RATIONAL R_0=1.0} LOWMEM
+c2: COORDINATIONNUMBER SPECIESA=11-20 SPECIESB=21-30 SWITCH={RATIONAL R_0=1.0} LOWMEM
+h: HISTOGRAM DATA=c1,c2 GRID_BIN=100,100 GRID_MIN=0,0 GRID_MAX=10,10 BANDWIDTH=0.1,0.1
+f: FOURIER_TRANSFORM STRIDE=1 GRID=h FT_TYPE=complex FOURIER_PARAMETERS=0,-1  
+
+DUMPGRID GRID=f FILE=f.grid FMT=%8.4f