Wrap users in a <span> of class "user" and with a data-user-id attribute

Makes user references selectable for styling and provides metadata about
the reference.
Tone down the visual prominence of user links in search results

By setting the font-weight and color to inherit, they pick up the
natural look of the search results instead of being bold and the color
depending on visited status.  For aileron, this means the links are
normal weight and always black.  Knowing if you've previously visited a
user summary page is not terribly useful, and the dual-toned links are
distracting in search results.  HTML in formats, such as <b>, can still
modify the links' appearance.
Adjust CSS layout so the full width is used for requestor accordion content

Floating the user summary link forced the width of the floated element
(the text "User Summary") to be unused by accordion content, effectively
producing a large right margin.

Use relative/absolute positioning to place the User Summary link in the
top right corner and preserve the accordion's full width.  Additionally,
adjust styles so the link behaves like a normal link and unlike the rest
of the accordion header.  This helps distinguish that "User Summary"
isn't just a static part of the header.
Merge branch '4.2/user-links-display'