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