refs #9194. Try replace custom DisjointElement
refs #9194. Get working with boost::disjoint_set.
refs #9194. Remove custom DisjointElement.
Revert "refs #9194. Remove custom DisjointElement."

This reverts commit 073d3cc41a8fb65c8fe16dea57d9975b8d408265.
Revert "refs #9194. Get working with boost::disjoint_set."

This reverts commit c33f672fd301ebba7dbba81742e4333f1d7bb86f.
Revert "refs #9194. Try replace custom DisjointElement"

This reverts commit 7b2bd126eba59fba68a4d114381c64e5ff8d14de.
refs #9194. Cleanup, document and speedups.
refs #9194. Minor tweaks around reporting
refs #9194. Document code better.
Merge branch 'feature/9194_connected_component_algorithm' into develop