BUG: Channel selection not preserved in web menu

[gavento]

Describe the bug
When a channel is chosen on the web as ..?channel=X, the links to other sections in top menu forget this parameter (so you see the main channel again).

To Reproduce
Steps to reproduce the behavior:

1. Go to http://epidemicforecasting.org/country-rt-estimates?channel=model
2. Click on any item in top menu
3. See that there is no channel selected in the URL

[witzatom]

since the ?channel parameter is a dev only/secret feature i would say this is low priority