Provide access to a server side state store from ui-templates

### Description

Currently there is no server side store accessible to ui-templates for the storage of state that must be maintained across a browser refresh. All that is available to the template after a refresh is the contents of the latest message sent to or from the template, so to get round the problem it is necessary to ensure that all messages sent to the node or sent from it include all the data necessary to restore the state after a refresh.
[This thread on the forum[(https://discourse.nodered.org/t/help-needed-dashboard-2-vue-reset-values-on-refresh/88393) illustrates the problem and the hoops that must be jumped through to solve it at the moment.

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate