wip, state & plugin

src/mol-plugin/command.ts

src/mol-plugin/context.ts

src/mol-plugin/providers/custom-prop.ts

src/mol-plugin/providers/theme.ts

src/mol-plugin/state.ts

src/mol-plugin/state/action.ts

src/mol-plugin/state/actions/basic.ts

src/mol-plugin/ui/tree.tsx

src/mol-state/context.ts

src/mol-state/state.ts

src/mol-state/tree.ts