wip, point representation, point shader fixes

src/apps/canvas/structure-view.ts

src/mol-geo/representation/structure/representation/point.ts

src/mol-geo/representation/structure/units-visual.ts

src/mol-geo/representation/structure/visual/element-point.ts

...resentation/structure/visual/polymer-backbone-cylinder.ts

src/mol-geo/representation/structure/visual/util/common.ts

src/mol-gl/renderer.ts

src/mol-gl/shader/chunks/assign-material-color.glsl

src/mol-gl/shader/chunks/common-frag-params.glsl

src/mol-gl/shader/chunks/common-vert-params.glsl

src/mol-gl/shader/mesh.frag

src/mol-gl/shader/mesh.vert

src/mol-gl/shader/point.frag

src/mol-view/theme/color/unit-index.ts

src/mol-view/viewer.ts