fix #782 grid lines on x axis are centered on selected warp mesh
fix #782 grid lines on x axis are centered on selected warp mesh

mrakitin/sirepo,mkeilman/sirepo,radiasoft/sirepo,radiasoft/sirepo,mrakitin/sirepo,mrakitin/sirepo,radiasoft/sirepo,mkeilman/sirepo,mkeilman/sirepo,mrakitin/sirepo,mkeilman/sirepo,radiasoft/sirepo,radiasoft/sirepo