auto-detect saved map json from archive.org collections (refactored version)

[7malikk]

Fixes #1343

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UI Changes

[7malikk]

@jywarren This is ready for a merge, after which I'd make a PR for the save button refactor It goes the full circle 😃

[7malikk]

All done @jywarren

[jywarren]

Done and merged, great job!