Feature/map clustering distance prop

[bgilhome-now]

Issue:
PR to accompany feature request #1290

What I did

• Added optional clusteringDistance prop to RplMap & passed it to ol-animated-clusterlayer in the template
• Added Map 'Clustering Nearer' & 'Clustering Disabled' stories to Storybook

How to test

• See the new stories in the Storybook and confirm clustering behaviour has changed

Checklist

For all PR's

• I've added relevant changes to the project Readme if needed.
• I've updated the documentation site as needed.
• I have added unit tests to cover my changes (if not applicable, please state why in a comment)

For new components only

• I have added a story covering all variants
• I have checked a11y tab in storybook passes
• Any events are emitted on the event bus

[dylankelly]

@bgilhome-now thanks for the PR, going to merge this into the 2.14.0 release, this is scheduled for this Thursday

Closes #1290