This PR does a few things. 
It fixes a shutdown-order flaw in the chainfreezer. Previously, the chain-freezer would shutdown the freezer backend first, and then signal for the loop to exit. This can lead to a scenario where the freezer tries to fsync closed files, which is an error-conditon that could lead to exit via log.Crit. 

It also makes the printout more detailed when truncating 'dangling' items, by showing the exact number instead of approximate MB.

This PR also adds calls to fsync files before closing them, and also makes the `db inspect` command slightly more robust.