icon tweaks

src/mol-plugin-ui/camera.tsx

src/mol-plugin-ui/controls/parameters.tsx

src/mol-plugin-ui/left-panel.tsx

src/mol-plugin-ui/state/snapshots.tsx

src/mol-plugin-ui/state/tree.tsx

src/mol-plugin-ui/structure/components.tsx

src/mol-plugin-ui/structure/generic.tsx

src/mol-plugin-ui/structure/measurements.tsx

src/mol-plugin-ui/viewport.tsx