Merge branch 'fileinfo'
histogram: Basic structure
histogram: Calculation of 2D histograms
histogram: Plotting of 2D histograms

The free energy landscape is plotted.
histogram: Calculation of 1D histograms
histogram: Calculation of 1D free energy landscape
histogram: Plotting of 1D histograms

The free energy landscape is plotted.
histogram: Calculate for lowest sampling time only
histogram: Reference file search improved (1)

Omit suffixes piece by piece to exactly match filenames.
histogram: Reference file search improved (2)

Search files with different sampling times if TIME_UNIT is set.