Remove legacy dvajs ; unblock react update

dvajs is legacy, unmaintained, poorly documented and preventing us from moving to a more recent react version. It is likely that modern react components mean we don't need it.

We are using it for routing, history, and redux connect. However there are warnings in the browser console that are likely from dva -

```txt
Warning: Please use `require("history").createHashHistory` instead of `require("history/createHashHistory")`. Support for the latter will be removed in the next major release.

Warning: componentWillMount has been renamed, and is not recommended for use. See https://fb.me/react-unsafe-component-lifecycles for details.

* Move code with side effects to componentDidMount, and set initial state in the constructor.
* Rename componentWillMount to UNSAFE_componentWillMount to suppress this warning in non-strict mode. In React 17.x, only the UNSAFE_ name will work. To rename all deprecated lifecycles to their new names, you can run `npx react-codemod rename-unsafe-lifecycles` in your project source folder.

Please update the following components: Route, Router, Switch
```