set .master for buildsteps
Add a .master to Build objects
don't rely on os.getcwd to get master basedir when looking for templates

Fixes #2586.
Append mode to renderables list in VisualStudio step
Merge branch 'enhancement_#2592' of git://github.com/dickymoe/buildbot
Merge branch 'build-master-attr' of git://github.com/djmitche/buildbot
Merge branch 'buildstep-master' of git://github.com/djmitche/buildbot

Conflicts:
	master/buildbot/test/util/steps.py

+autopep8