Milo: Add an option to hide green steps

milo/appengine/buildbot/expectations/win_chromium_rel_ng.246309.build.json

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     "Label": "#246309",
     "Status": "Failure",
     "Bot": {
       "Label": "vm774-m4",
@@ skipping 48 matching lines @@
             "Label": "preamble",
             "URL": "http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_ng/builds/246309/steps/steps/logs/preamble"
           }
         ]
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       "Started": "2016-06-27T23:30:30.081103104Z",
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       "Type": "Recipe",
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+      "Verbosity": 2,
       "Text": [
         "running steps via annotated script"
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     },
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       "Label": "update_scripts",
       "Status": "Success",
       "MainLink": [
         {
           "Label": "stdio",
@@ skipping 502 matching lines @@
             "Label": "json.output",
             "URL": "http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_ng/builds/246309/steps/compile%20%28with%20patch%29/logs/json.output"
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       "Finished": "2016-06-27T23:36:30.258343936Z",
       "Duration": 132432765952,
       "Type": "Recipe",
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-      "Verbosity": 0,
+      "Verbosity": 2,
       "Text": [
         "compile (with patch)"
       ]
     },
     {
       "Label": "taskkill (2)",
       "Status": "Success",
       "MainLink": [
         {
           "Label": "stdio",
@@ skipping 393 matching lines @@
         "URL": ""
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