- Split up process cache in FileBackend into separate arrays for expensive and inexpensive entries. Put the local reference FSFile object cache in the former since it takes up disk space on /tmp.
- Removed FileBackendBase::resolveWikiId(); doesn't really work well with FileBackendMultiWrite and the functionality is best handled in resolveContainerName(). Follows-up r108303.
- Gave FileOp::doAttempt() a default implementation (a no-op) to be more libertarian.
- Some documentation tweaks.