Switches to using a single table for many repos instead of multiple databases.
Changes the headbookmarks table to be a pushkeys table using the pushkeys
namespace convention.
Move public phase boundary forward during sync
Thread syncdb so we pull from the db at the same time we are writing to the
revlogs. Also use a buffered revlog so we only flush at the very end.
Clear repo._filecache after syncing in order to force the changelog to update.
