Alias repairDatabase/repair to rebuildDatabase/rebuild

We have two different use cases for doing a "repair":

• Unclean shutdown, no good backup nor replicas, and you want to recover to a working state (understanding you may lose data)
• Compaction and/or rebuilding the db files

The docs cover and warn about the first case, but if you are doing the second those warnings are confusing and inappropriate. It is also very confusing to tell or explain they need to do a repair when really we want them to do the second thing.

We may want to deprecate and remove repair/repairDatabase in the future as well.