Fix support for elements that have several tpsvg: special attributes
applied; for example an element can have both tpsvg:anchor="bottom" and
tpsvg:anchor="right". Previously only one of the special attributes
would have actually had effect.
Fix / enhancement to handling of arcs (specifically, arcs that are
specified using the 'a' / 'A' command). If an arc is the only element in
a path (or path segment), the arc is represented as an arc object which
enables it to be manipulated programmatically in terms of start and
sweep angle (which I use to perform gauge animations). Otherwise, it
forms part of a more complex path. Previously, arcs were always stored
as dedicated arc objects in isolation, meaning that complex paths that
used them were disjointed and broken.