Revert "removed all browser-specific gradients as the recently (in 42ff6730) introduced svg makes them unnecessary"

This reverts commit dbd59867.

the new template allows to use a favicon in media/wiki/favicon.ico so we
should support uploading it as well.

See
http://stackoverflow.com/questions/805107/how-to-create-multiline-strings
for info on them.

We had a lot of options lumped together under "Advanced Settings". I
introduced two more categories and move a few options to other existing
categories.
I also reordered the appropriate entries in the source files to make it
easier to find stuff when extending the options.

We had a lot of options lumped together under "Advanced Settings". I
introduced two more categories and move a few options to other existing
categories.
I also reordered the appropriate entries in the source files to make it
easier to find stuff when extending the options.