This CL imports the bot_update script, along with the bot_update and gclient recipe modules from build. This should allow for recipes to run on swarming.

Also moves the recipe stuff into the infra folder.

bot_update has been modified. See full diff at https://paste.googleplex.com/4969207737352192

TBR=phajdan.jr@chromium.org

BUG=

Review URL: https://codereview.chromium.org/1641363002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298490 0039d316-1c4b-4281-b951-d872f2087c98