Arvados

This functionality will allow to place tooltip anywhere within the application with custom messages that can help new users to discover wb2 functionalities easier. This option should allow users to disable it when they decide that it is no longer required. Functionality will be delivered by the external library which will be loaded on the first load of the wb2 application from a remote source (this allows to provide very business specific tooltip messages)

Things to consider:
- How to structure/create the code in order to allow easy identification for the tooltip (custom data attributes?)
- Where should be the link for the custom tooltip library specified
- How we expose/document all available tooltip anchors (places where tooltip can be added)
- How ensure that the tooltip is displayed properly and do not cover important parts (functionality to remove tooltip - maybe on click)?

Applied in changeset arvados-workbench2|273119605b7f33940a5ef9b1422eb1ff152d6764.