Rsync and dumpstats

Preliminary pull request. It does two things, makes rsync work better with fusedav, and dumps stats on shutdown to better enable analysis. Some things I'd like to see, and some caveats:
1. After rsync, the files on the binding used will have the timestamps of the files on the local host. This should make redoing rsync more efficient.
a. However, in a multi-drop environment, the timestamps on the second drop after propfind will have the timestamp of the current time.
b. So this fix is more useful in a single-drop environment, but that suits dev and test, where most rsync activity will happen (?)

2. dump stats on shutdown will dump the stats similar to kill -SIGUSR2 <pid> (currently, the statcache walk is not done). This should make it easier to see if we can correlate memory and BUMP&FETCH stats. In particular, it might be able to correlate a pattern of access with performance/memory issues.
a. Better yet would be to also dump the heap stats. For this to happen we would need to build and deploy a version of jemalloc which enables this heap stat collection, and make our standard fusedav mount be the same as what we now have for fusedavje.
b. We could dump stats on a periodic basis, say every day, or every week, which would make the heap dump more useful. We would also need to add a cleanup thread.

Comments?