Fix category block status without negative score

Categories without blocking or approval scores will
result in the blocking/approved image appearing
in the category column after changes are merged
should the score by the reviewer match the minimum
or maximum value respectively.

Add check to ignore "No Score" values of 0.

Fixes bug 980927

Change-Id: I29d8d6653a90cd8f80dcb2955fac90662142042e
Add outdated color option

Recommend we set this to #F5CCCC

Fixes bug 980976

Change-Id: I74f384f48ea2eb6a75efd0a79e0143d33d0d80a7
Add Work In Progress state to Gerrit.

This adds a new button that allows an authorized user to set a
change to Work In Progress, and a button to change from WIP back
to a "Ready For Review" state. Any change in the WIP state will not
show up in anyone's Review Requests. Pushing a new patchset will
reset the change to Review In Progress. A new "Work In Progress"
permission is also added. Drafts are not allowed to be set to
Work In Progress.

Besides the button, one can also set a change to WIP with the
"gerrit review" command:

   ssh -p 29418 user@host gerrit review --workinprogress <id>

And back to reviewable:

   ssh -p 29418 user@host gerrit review --readyforreview <id>

The "gerrit review" command documentation is updated for these
new options, too.

Email will be sent when status is changed to Work In Progress,
or when changed back to a reviewable status.

Change-Id: Ide6c5e4dcf6cee826aa2614862dc34bb99a52c7a