Persist admin menu state to browser storage to ensure quicker render of menu.

[getdave]

We should cache the admin menu data returned from the API endpoint in order to ensure the most suitable menu is rendered near-instantly upon Calypso UI load.

To do this we can use the higher order reducer [withSchemaValidation](https://github.com/Automattic/wp-calypso/blob/ab54e0ce137c96ed697e3d35eb13b8f9698ffc0d/client/state/utils/schema-utils.js#L98 ) providing a suitable schema for the data structure we expect to receive from the API endpoint.

This should cause the data to be cached in browser storage and refreshed as required.

[getdave]

Note that the entire Redux state is not persisted to the browser. In order to persist state in browser storage the reducer must be wrapped with withSchemaValidation as instructed below.

See https://github.com/Automattic/wp-calypso/blob/master/docs/data-persistence.md