Revert 9 commits specific to patch panels

This reverts the following commits (no conflicts):

6071555
cf54c36
bfce8a3
2381357
d884661
f129eb6
a4b6536
68dc69c
597896f
Revert "- rebase against master branch"

This reverts commit 6a40d076dea1442abe4f32bd48b9534e2029e7b0.

Conflicts:
	ChangeLog
	wwwroot/inc/upgrade.php
Revert 2 commits specific to patch panels

This reverts the following commits (no conflicts):

f9ea479
764aa01
Revert "add support for one-to-many port links, and cable path tracing"

This reverts commit a73909424b27e3631d80ab949ad3030c7b06d305.

Conflicts:
	README
	wwwroot/inc/install.php
	wwwroot/inc/popup.php
	wwwroot/inc/upgrade.php
fixup the next release version (0.21.0 -> 0.20.6)