Code review comment for lp:~wgrant/launchpad/sprb-new-model-columns

This branch extends the prerequisite DB branch by adding the new dependencies, upload_log and pocket columns to the SourcePackageRecipeBuild model class. It also moves Build.storeUploadLog onto BuildBase, where it can be used by SPRB.

I had to alter BuildBase.storeBuildInfo to explicitly turn the dependencies str into a unicode, since plain Storm is less forgiving than its SQLObject compatibility layer. Since the method didn't appear to be tested anywhere, I've added some unit tests for the dependencies behaviour.