WIP - Collection map type implementation

[dmfalke]

This is a work in progress.

Closes #241

This PR adds the implementation of a collection variable map type for bar plot markers.

Current status of work:

• Some more refactoring to make marker configuration more generic
• Implement configuration menu
• Implement overlay components and marker hooks
• Move HeaderButtons and related logic to its own component that is called by each maptype plugin. (Ie, remove references to marker config from MapAnalysisImpl.)
• Need to factor logic out of several react hooks so that they can be used in non-hook contexts. This is a peril of using react hooks, since they are not portable.