Simplify the Block Jacobi and Schur Jacobi preconditioners.

1. Extend the implementation of BlockRandomAccessDiagonalMatrix
by adding Invert and RightMultiply methods.

2. Simplify the implementation of the Schur Jacobi preconditioner
using these new methods.

3. Replace the custom storage used inside Block Jacobi preconditioner
with BlockRandomAccessDiagonalMatrix and simplify its implementation
too.

Change-Id: I9d4888b35f0f228c08244abbdda5298b3ce9c466
9 files changed