[DOC 2.2.0] Uninstall followed by re-install may leave xdcr _replicator database intact causing badness

It was found that in installations with custom data path uninstall doesn't clean up anything. And then it's possible as part of installation to choose same data path.

All database files will be deleted in the process, but _replicator database will be left intact. Which will cause node to think it still have those old XDCR replications it had before uninstall. This will cause tons of internal crashes and UI confusion.

For 2.1.0 we'll document workaround. If you're doing uninstall followed by reinstall, make sure to manually delete _replicator.couch.1 file from data directory before reinstalling.