The main goal of this patch is to cleanup the interface of every modifier. More specifically the interface of modifiers should be DerivedMesh-free. Internally some modifiers still use DerivedMesh. However I think it is better when the wrappers are in the modifiers so that higher level functions can use the simplified interface. This patch removes the applyModifier_DM and applyModifierEM_DM functions. In a previous patch (rB3614d9d) the other functions that used DerivedMesh have been removed. Reviewers: brecht