Command line is saved in profile file

The full command line of what was run during the profiling is now
saved into the profile file. It is used to set the graph title with
'mprof plot'.
Plot all memory usage information

Memory usage when entering and leaving a function is now included
with the other measurements. This fixes some discrepancies between
brackets and curves when sampling frequency was low.

Add an option to prevent displaying of timestamps in plots
(mprof plot -n)