mol-plugin: state manager

src/mol-plugin/behavior/static/state.ts

src/mol-plugin/command/state.ts

src/mol-plugin/context.ts

src/mol-plugin/state.ts

src/mol-plugin/state/snapshots.ts

src/mol-plugin/ui/camera.tsx

src/mol-plugin/ui/controls.tsx

src/mol-plugin/ui/plugin.tsx

src/mol-plugin/ui/state.tsx