1-way delay and improvements for heterogeneous measurement

Important changes are:
e7987d1 Add 1-way delay measurement
e4f9677 Unique identifier for intermediated interval report columns
706be33 Determine unit of Kernel TCP metrics automatically
4d911fb Undo commit 517fda8 (add option -Z)
9d97a22 Use a function call to hide/show intermediated interval report columns
dc6e5fe Use a function call to change the unit of intermediated interval repo…
c5f7078 Column visibility based on involved OSes
61b4096 Enable 1-way delay measurement only when configured with --enable-debug