[cas] fix for Derivative[f(x)+g(x)] (also add floor() ceiling() properly)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37576 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[cas] use ggbans instead of lots of %0

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37577 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e