Old Icecast versions (lower than 2.4.0), all current icecast-kh versions
and derivates of that like the AzuraCast kh-ac fork do not treat the
HTTP headers in the response as case-insensitive even though this is
required by the HTTP RFC.
Go by default canonicalizes the Headers, to prevent that and actually
write our case-sensitive keys we need to access the map directly.
This adds a helper that does so, tests for the helper and uses the
helper in the relevant places in yp.go.

Marvin Scholz authored May 06, 2020 and Andreas Mieke committed May 06, 2020

Fix #11

Fixes #5

Fixes #8

The following order is used: ',', '/', ' '

See #9

See #8

Codecs and Genres overview pages now ordered by count of Streams for that Codec/Genre
Codec and Genre detail pages ordered now by listen count
Also changed behaviour for Genres with / or special characters