* Precedence: explicit selection -> provider preference -> last selection -> first/default value.
* Remove logic to bail out on retrigger

VSTHRD103 reminds people not to use .Result in tasks, which is great
advice but we get a few false positives; in particular our
SafeContinueWith extension isn't understood by the analyzer that the
tasks involved are always completed, so you can just .Result them.
Rather than working around this, let's just disable the analyzer in
those cases.

Been almost a month since the code formatter was run so this change was
a bit larger than would be expected for a normal (weekly) update.  Diffs
mostly around:

- Whitespace changes
- Missing copyright headers
- Missing visibility modifiers

     * Gray background
     * No border
     * No padding on top or right
     * Colored bar at bottom of dashboard

     This requires us to set UseLayoutRounding=True, since we're trying to draw straight lines (https://msdn.microsoft.com/en-us/library/system.windows.uielement.uselayoutrounding%28v=vs.95%29.aspx). (changeset 1411219)