Implement a blocked upper-bidiagonalization algorithm. The computeUnblocked function is currently for benchmarking purpose.
Use unblocked version if the matrix is too small, plus some cleaning.
Fixed InnerPanel definition in the Transformation class.
Added some inital documentation on InnerPanel.

--HG--
extra : rebase_source : 6fca5da4aca3bf6463fb30a47e763046722461d1
Added missing inline statements in order to prevent linker errors.
BDCSVD: Use rational interpolation to solve secular equation.
Algorithm is rather ad-hoc and falls back on bisection if required.