Render 'env' for source steps

Fixes #2610.
Correct documentation typo regarding MsBuild import.
Merge branch 'master' of git://github.com/DavidKeller/buildbot
Fix decode comments
Fix tests
Merge branch 'fix_comments_decode' of git://github.com/Ratio2/buildbot
Revert "Merge branch 'SlaveInfo' of git://github.com/jaredgrubb/buildbot"

This reverts commit 1c5973413aa3b7e5f2f197b488cd58206b7ac057, reversing
changes made to bf5c148e7b427c1f685ce846696a90ed2dc24704.

See https://github.com/buildbot/buildbot/pull/880 for details on why
this was reverted.

Conflicts:
	master/buildbot/status/slave.py
	master/docs/relnotes/index.rst
restore 'gerritchangesource: use gerrit's changeid as the branch' (ccf6c117)
add buildbot.util.asyncSleep
Add an integration test for try scheduler client/server interactions.

This runs a full master with real builds.

Waiting for SSH builds does not work - the buildmaster returns buildset
ID's, while the client expects its external_idstring, so it waits
forever.  This functionality will be difficult to support as-is in nine,
so it's been removed.
Merge branch 'restore-gerrit-changeid-in-branch' of git://github.com/djmitche/buildbot (PR #1024)
Merge remote-tracking branch 'origin/8/try-integration-test' (PR #1026)

+autopep8
clean up changes to try scheduler
Merge branch '8/trysched-cleanup' of git://github.com/djmitche/buildbot (PR #1027)
Add a BufferLogObserver and use it in SetPropertyFromCommand
Merge branch '8/bufferedlogobserver' of git://github.com/djmitche/buildbot
support pylint-1.1.0
tweak relnotes
don't let printStatus produce unexpected results
Add 'pollAtLaunch' flag for polling change sources

This allows a poller to poll immediately on launch and get
changes that occurred while it was down.