Use reference qualifiers to avoid reference to temporaries

Until now one could write code like

  auto&& jt = AffineGeometry<...>(...).jacobianTransposed(...);

This compiles and (depending on the surrounding code)
may even lead to the expected results. However, since
AffineGeometry hands out a reference to the stored
matrix jt is a reference to a temporary that may
be overwritten by other stack variables.

By explicitly deleting the overload for r-values the compiler
rejects the above code and only allows to call jacobianTransposed()
on l-values.
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