Revert of Removed virtualenv from depot_tools (patchset #1 id:1 of https://codereview.chromium.org/1437483002/ )

Reason for revert:
This CL over-aggressively removed the Windows bootstrap code used by /gclient.bat, which in turn downloads/installs the Windows toolchain, including Python. Labs can no longer provision Windows bots because of this.

update_depot_tools.bat did more than initialize the virtualenv. It also downloaded and installed Python, Git, and Subversion on Windows systems.

I'm reverting to restore the toolchain so we can create new Windows bots.

Original issue's description:
> Removed virtualenv from depot_tools
>
> This effectively reverts http://crrev.com/1195423002 and
> http://crrev.com/1205873002.
>
> R=pgervais@chromium.org, tandrii@chromium.org
> TBR=pgervais@chromium.org  # i wanna get my Fixit credit today :-)
> BUG=542922,503067
>
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=297491

TBR=pgervais@chromium.org,tandrii@chromium.org,sergiyb@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=542922,503067

Review URL: https://codereview.chromium.org/1431173002 .

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@297493 0039d316-1c4b-4281-b951-d872f2087c98

This effectively reverts http://crrev.com/1195423002 and
http://crrev.com/1205873002.

R=pgervais@chromium.org, tandrii@chromium.org
TBR=pgervais@chromium.org  # i wanna get my Fixit credit today :-)
BUG=542922,503067

Review URL: https://codereview.chromium.org/1437483002 .

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@297491 0039d316-1c4b-4281-b951-d872f2087c98

Clean up stray spaces.

TBR=iannucci@chromium.org
BUG=241769

Review URL: https://codereview.chromium.org/72783002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@235145 0039d316-1c4b-4281-b951-d872f2087c98

Set svn:eol-style=CRLF for all .bat files and everything in bootstrap/win/
Set svn:eol-style=LF for everything else.

Also delete depot_tools/git_cl/ since it's not used anymore.
Review URL: http://codereview.chromium.org/8055016

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@103051 0039d316-1c4b-4281-b951-d872f2087c98

Review URL: http://codereview.chromium.org/99233

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@14970 0039d316-1c4b-4281-b951-d872f2087c98

TBR=skylined
Review URL: http://codereview.chromium.org/102004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@14760 0039d316-1c4b-4281-b951-d872f2087c98

Review URL: http://codereview.chromium.org/92150

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@14466 0039d316-1c4b-4281-b951-d872f2087c98

Actually, the get_file.js code was written by B.J. I have no merit.
Review URL: http://codereview.chromium.org/93139

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@14457 0039d316-1c4b-4281-b951-d872f2087c98