LocalStatus as SQLlite

[stewart@xxxxxxxxxxxxxxxx]

About a year ago I sent to the list a patch that switched LocalStatus
from the flat files to an SQLLite database which for me, improved
speed and memory usage (the latter being the most dramatic).

A year later, I'm still using and maintaining my patches.

So here's the latest. Nothing much changed from the last patches,
but they are updated to the latest git tree.

I've also pushed to http://saturn.flamingspork.com/~stewart/offlineimap
the branch sqlite_localstatus