ref #80: new scan branch with fix for delayed indexing
fix a couple of typos
ref #80: add a couple of debug lines
ref #80: delete missed messages after they've been collected
ref #80: missed a filter
ref #80: missing part improvements
fix an error with catching thread timeouts
ref #80: scanning improvements
fix a couple of log lines
ref #80: rewrite update/backfill into scan function
ref #80: minor bugfix: was collecting 1 extra message per iteration
ref #80: fix new group scan
ref #80: remove debug values
ref #80: disable miss-checks on backfills and fix SA in-pred warning
fix a  bug when finding posts by date
fix that same bug, more robustly this time
ref #80: add some extra logging to show how many iterations of scanning is left

not that useful for updates, but should be for backfills
changes config: fixes #81: introduce variable query windowing for binary processing

 no need to do it for release processing, which loads a much smaller set of data into memory. see comments above both functions.
change segment/part ids to use big integers, since we're starting to overflow them
modified db.py for bigints