[giac] add regroup() to Length[]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36562 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
* Remove reference to missing image from GWT advanced
* Hide CAS if Android version < 4.4

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36563 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Do not init GIAC on Android < 4.4

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36564 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e