tasks #7122 Color variable managment

* rename orange in main
* add navbar-color variable
* rename dark-orange in dark-main
* add navbar-color-hover variable

Change-Id: Ic538447961ef93aa078a4a4ca106abef42841fdf
Merge commit 'refs/changes/91/2691/1' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  tasks #7122 Color variable managment
This is Tuleap 7.2.99.3

Change-Id: I249eb1c0ff316557838868538fe63f9a1a792e7b