Update for GHC 7.8
Avoid 'hash' since it's not a pure function anymore
Build on GHC 7.6 as well as GHC 7.8
Experimental implementation of DB staging
Store staged updates in a separate database
Use an in-memory database for staged updates and commit in sorted order
Drop indices while inserting staged updates
Enable in-memory staging database (which turns out to be slower, but the refactorings are still desirable)