Issues #1399

Summary

Random color for clustering and markers are only have luminance of 40 and higher so clustering text is easier to read with new
Clustering Radius slider was added so that clustering can be adjusted to the desired rate. Defaults to the lowest it can be

[x] There is a description section in the pull request that details what the proposed changes do. It can be very brief if need be, but it ought to exist.
[x] Hotfixes should be branched off of the master branch and squash and merged back into the master branch.
[x] Features and backlog bugs should be merged into the Development branch, NOT master
[x] All new text is preferably internationalized (i.e., no end-user-visible text is hard-coded on the PHP pages), and the spreadsheet tracking internationalizations has been updated either with a new row or with checkmarks to existing rows.
[x] There are no linter errors
[x] New features have responsive design (i.e., look aesthetically pleasing both full screen and with small or mobile screens)
[x] Symbiota coding standards have been followed
[x] If any files have been reformatted (e.g., by an autoformatter), the reformat is its own, separate commit in the PR
[x] Comment which GitHub issue(s), if any does this PR address
[x] If this PR makes any changes that would require additional configuration of any Symbiota portals outside of the files tracked in this repository, make sure that those changes are detailed in this document.

[x] It is the code author's responsibility to merge their own pull request after it has been approved
[x] If this PR represents a merge into the Development branch, remember to use the squash & merge option
[x] If this PR represents a merge from the Development branch into the master branch, remember to use the merge option
[x] If this PR represents a hotfix into the master branch, a subsequent PR from master into Development should be made merge option (i.e., no squash).
[x] If the dev team has agreed that this PR represents the last PR going into the Development branch before a tagged release (i.e., before an imminent merge into the master branch), make sure to notify the team and lock the Development branch to prevent accidental merges while QA takes place. Follow the release protocol here.
[x] Don't forget to delete your feature branch upon merge. Ignore this step as required.

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