Don't clip left or right-hand sides, only top and bottom (which are what need clipping to hide exctra height/depth, and prevent the positioning spans from overlaying the material above).  Resolves issue #807, and may hekp issue #646.
Use proper value of base scaling to reset u and v in super- and subscript positioning.  Resolves issue #804.
Preserve RDFa and other non-standard attributes from MathML elements in the HTML-CSS or SVG output.  Resolves issue #860, and also handles #502 as a side-effect.
Merge branch 'issue807' into develop.  Issue #807.
Merge branch 'issue804' into develop.  Issue #804.
Merge branch 'issue860' into develop.  Issue #860.