added option to ignore hydrogens in structure representations

src/mol-math/geometry/common.ts

src/mol-math/geometry/gaussian-density/cpu.ts

src/mol-math/geometry/gaussian-density/gpu.ts

src/mol-math/geometry/molecular-surface.ts

src/mol-repr/structure/visual/carbohydrate-link-cylinder.ts

...r/structure/visual/carbohydrate-terminal-link-cylinder.ts

...ol-repr/structure/visual/cross-link-restraint-cylinder.ts

src/mol-repr/structure/visual/element-point.ts

src/mol-repr/structure/visual/element-sphere.ts

src/mol-repr/structure/visual/gaussian-density-volume.ts

src/mol-repr/structure/visual/gaussian-surface-mesh.ts

src/mol-repr/structure/visual/gaussian-surface-wireframe.ts

src/mol-repr/structure/visual/inter-unit-link-cylinder.ts

src/mol-repr/structure/visual/intra-unit-link-cylinder.ts

src/mol-repr/structure/visual/molecular-surface-mesh.ts

src/mol-repr/structure/visual/util/common.ts

src/mol-repr/structure/visual/util/element.ts

src/mol-repr/structure/visual/util/gaussian.ts

src/mol-repr/structure/visual/util/link.ts

src/mol-repr/structure/visual/util/molecular-surface.ts