Ensure a unified system for status-based issue coloring throughout the UI

There are a number of places that we want the UI for project_issue to use color-coding based on the issue status:

• The issue queue views #1549276: Port default issue queue views to views 7.x-3.x
• The [#xxx] issue link filter #1624874: Port project issue text filter
• The issue nid field formatter #1628160: Port issue nid field formatter to D7
• Displaying the status in the issue metadata block #1696872: Create a block that shows the issue metadata (in particular #1721776: Figure out how to render the status field with markup that includes the status value as a class)

We need a consistent, unified system for this. Basically, all of these places need to use the same CSS classes on the appropriate wrapper HTML elements, and the CSS should be written in such a way that we only define the colors for each class once.

Note: I'm explicitly *NOT* talking about #1721768: Allow site admins to associate colors for issue status values via the UI here. Once we ensure that all the color handling stuff is unified, we can contemplate making it possible to define those colors via the UI. For now, I'm happy to leave some default colors in project_issue.css and let sites override via their theme as needed. But, it's essential that we don't have 4 sets of colors for those 4 different places that we use status-based coloring in the UI, and it'd be nice if you only needed a single CSS selector to define each status color.