Add ability to pause build-slaves.

Signed-off-by: Tom Prince <tom.prince@ualberta.net>
Start implementing option to pause a slave.

Signed-off-by: Tom Prince <tom.prince@ualberta.net>
Refactor code for clobberOnFailure. Don't clobber() for this case, use independent functions
Don't allow git source step to make shallow in any mode other than clobber

Fixes #2154
- New WIP for Clean shutdown.
fix typo
steps: added support for VS2012 via msbuild

 - the step is called MsBuild as the same code would work for VS2010
   (barring the environment variable name)
 - this new step allows for building drivers as the new Windows Driver Kit 8 integrates into VS2012
   (you can target Vista, Win7 and Win8)
Also decode the filed names when force-building.

With ForceScheduler, it is possible to have semi-arbitrary names. This
also cleans up the arg-preprocessing code somewhat.

Refs #1054.
Allow forcing on multiple builders at once.

The web status currently does this by forcing multiple times, once for each builder,
creating a separate buildset for each. Instead, teach ForceScheduler to support
starting multiple builders in a single buildset, and refactor the webstatus code to
support that.

Fixes #2342.
steps: refactored MsBuild step according to review comments
steps: removed junk from an old rev (proper merge)
steps: removed another couple of uneeded changes
MsBuild: minor cleanups
msbuild: added a minimal unit test
steps: extended docs with MsBuild details
pyflakes and whitespace
Merge branch 'pull532'
Fix capitalization of Python
Fix "Pythons" -> "Python's"
Fix capitalization of Mercurial