FLUID-5457, FLUID-5469: Remove FSS

Removed FSS. The fss directory in the prefs framework is still there and will be addressed by [FLUID-5482](http://issues.fluidproject.org/browse/FLUID-5482)
http://issues.fluidproject.org/browse/FLUID-5469

Also adds a fix for FLUID-5457, which allows for the cross to appear when using a custom default theme.
http://issues.fluidproject.org/browse/FLUID-5457
Turns our Anastasia has fixed almost all broken links in http://issues.fluidproject.org/browse/FLUID-5523, except this one: https://github.com/fluid-project/infusion/blob/master/tests/manual-tests/components/inlineEdit/rich/json/config.json#L11

Can we fix it in this pull request. Thanks.