first version of the on screen keyboard (for tablet)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@35538 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Variable resolving simplification

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@35539 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fix for Derivative[ g(sin(x)),4 ]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@35540 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e