Blender Git Loki

minor edits to mesh operators

- Rename 'mesh.select_nth' operator menu item 'Every N Number of Verts' to 'Checker Deselect',
since its not just de-selecting verts (works on edges and faces too) and the term 'checker' gives a better description of the result.

- Rename 'mesh.select_by_number_vertices' to 'mesh.select_face_by_sides', since this is a face selection tool, which wasnt obvious from its name.

also remove dissolve by type menu since the option has been removed from the operator and was giving an error.