add a BuildStep.isNewStyle method
Merge branch 'master' into nine

Conflicts:
	master/buildbot/process/buildstep.py
	master/buildbot/test/unit/test_process_buildstep.py
relnotes for new-style steps
Merge branch 'master' into nine

(with minor modifications to documentation for nine)
support calling run on new-style steps
Merge branch 'master' into nine
Integration tests for custom buildsteps (backport from nine)

This includes updates to fakes and interface tests for them
Merge branch 'master' into nine