add a "using MKL" documentation page, add a minimal documentation of PARDISO wrapper classes, refine a bit the EIGEN_USE_* logic

- include MKL headers outside the Eigen namespace.

* * *
License disclaimer changed to BSD license for MKL_support.h
* * *
Pardiso support fixed, test added.
blas/lapack tests fixed: Scalar parameter was added in Cholesky, product_matrix_vector_triangular remaned to triangular_matrix_vector_product.
* * *
PARDISO test was added physically.

 - all what's not in unsupported/ is considered stable API
    (except internal stuff e.g. expression templates).

- mv Array/* into Core/
- merge Functors.h files, and move Norms.h into Dot.h

* add a new Eigen2Support module including Cwise, Flagged, and some other deprecated stuff
* add a few cwiseXxx functions
* adapt a few modules to use cwiseXxx instead of the .cwise() prefix

* improve Experimental.dox
* update urls from /api/ to /dox/

* remove all what was marked deprecated

of Eigen, and add a MSVC-friendly path in StaticAssert.

 * rename Cholesky to LLT
 * rename CholeskyWithoutSquareRoot to LDLT
 * rename MatrixBase::cholesky() to llt()
 * rename MatrixBase::choleskyNoSqrt() to ldlt()
 * make {LLT,LDLT}::solve() API consistent with other modules

Note that we are going to keep a source compatibility untill the next beta release.
E.g., the "old" Cholesky* classes, etc are still available for some time.
To be clear, Eigen beta2 should be (hopefully) source compatible with beta1,
and so beta2 will contain all the deprecated API of beta1. Those features marked
as deprecated will be removed in beta3 (or in the final 2.0 if there is no beta 3 !).

Also includes various updated in sparse Cholesky.

Documentation:
 * add an overview for each module.
 * add an example for .all() and Cwise::operator<

To try it with the unit tests set the cmake variable TEST_LIB to ON.

-fix CMakeLists, public headers weren't getting installed

extended cache optimal product to work in any row/column
major situations, and a few bugfixes (forgot to add the
Cholesky header, vectorization of CwiseBinary)