Merge lp://staging/~michael.nelson/launchpad/567922-binarypackagebuild-packagebuild into lp://staging/launchpad/db-devel

This branch is part of a pipeline for

https://blueprints.edge.launchpad.net/soyuz/+spec/build-generalisation
https://dev.launchpad.net/LEP/GeneralBuildHistories

In particular, this branch updates the IBuildFarmJob/IPackageJob interfaces and implementations so that items currently exported on IBinaryPackageBuild will continue to be exported when (in the next branch) the implementation of IBinaryPackageBuild switches to use the new tables.

It is dependent on the pending schema patch in a previous branch.

To test
=======

First update the test db schema (required as the db patch still needs to be updated to remove the old build table):
psql launchpad_ftest_template -f database/schema/pending/michaeln-build-generalisation.sql
bin/py database/schema/security.py -d launchpad_ftest_template

And then:
bin/test -vvt test_packagebuild -t test_buildfarmjob -t doc/build.txt -t test_buildqueue -t test_sourcepackagerecipebuild -t test_buildpackagejob

The next stage will be to add the methods currently defined for IBinaryPackageBuild to IBuildFarmJob/IPackageJob before switching the BinaryPackageBuild from the old build table to the new binarypackagebuild table.