Add a createMesh function to LayerData::Layer that creates a mesh from a layer
Add a createMesh function to LayerData::Layer that creates a mesh from a layer

Contributes to #52

ad1217/Cura,fxtentacle/Cura,fxtentacle/Cura,markwal/Cura,bq/Ultimaker-Cura,bq/Ultimaker-Cura,hmflash/Cura,fieldOfView/Cura,ynotstartups/Wanhao,senttech/Cura,ad1217/Cura,senttech/Cura,Curahelper/Cura,quillford/Cura,markwal/Cura,quillford/Cura,totalretribution/Cura,fieldOfView/Cura,totalretribution/Cura,ynotstartups/Wanhao,DeskboxBrazil/Cura,lo0ol/Ultimaker-Cura,lo0ol/Ultimaker-Cura,Curahelper/Cura,hmflash/Cura,DeskboxBrazil/Cura