[eigen] Student contribution: Pull Request

[BRUN Gauthier <brunga@xxxxxxxxxxxxxx>]

Hello,
Our project is in progress, today we would like to do a pull request.

The content of our commit is: Factorization of the JacobiSVD class into 
a SVDBase
class to prepare the arrival of the BDCSVD (Bidiagonalisation Divide 
and Conquer algorithm) class

We took in consideration the advices from Gael Guennebaud:
- the Base class is called SVDBase,
- we increased the proportion of shared code, from allocate atm, we 
didn't factorized
   code from compute atm because the BDC algorithm is not yet finished.
- we factorized tests, but it is not included in this commit, it will 
be the subject of the next commit.
- we checked our .emacs, we should have no more diff with indentation
- concerning the use of "this->", i tried using 
SVDBase<..>::m_attribut, but it didn't worked

We tested our commit with gcc 4.7.2 on Linux and we passed the tests.

Any feedback about our commit would be great for us.

Here is bitbucket from where we will do our pull request :

https://bitbucket.org/gl27/eigen-bdcsvd


(i wanted to put the diff here but i think it's too long)

this is our working bitbucket: https://bitbucket.org/gl27/eigen
In there we have the beginning of out BDCSVD.h
we have factorized the svd tests and added bdcsvd tests
we have added a benchmark to check SVD performances


Best regards,
Team GL27
Gauthier Brun, Nicolas Carre, Jean Ceccato, Pierre Zoppitelli