Major refactoring of picoharp code and add PT3 support
dump_pt2: Fix format
dump_pt3: Initial commit
picoharp: Add #pragma once
Makefile: Fix all rule
extract_pt2_timestamps: Add pt3 support
Makefile: Define default DESTDIR
plot-bins: Be more cautious about masking exceptions
read_photons: Import numpy
read_photons: Fix pt2 jiffy

This is quite bad as previously the jiffy was a factor of 4 too small
(1ps instead of the correct 4ps)
read_photons: Add pt3 support
dump_pt[23]: Dump jiffy