various style and comment cleanups
bring DB get_id functions up a level
duplicate less work in historical download/save pipeline
make a universal setting for the DB date format
yield the most recent bar's datetime from pipeline instead of rereading it from disk
Cache last updated times before saving to DB instead of committing each individually. Historical updates are network-bound again.
tweek historical batch sizes/sleep times for better performance without pissing Yahoo off
unify Watchlist into Instruments
move most of the data management code into its own folder
rename historicalmanager.py and DataReader/DataUpdater to historical.py and Reader/Updater respectively
move loading providers into providers/__init__.py
some import and comment cleanups
use a factory for getting data provider plugins