Block Preconditioner Framework

Contents:
1) BlockPreconditioner abstract class (define an interface),
2) TekoPreconditioner abstract class (common base for Teko preconditioner),
3) LSCPreconditioner (LSC preconditioner for Navier-Stokes with Teko)
Update the framework to the new changes in EpetraPreconditioner
New classes:
1) MatrixBlock to manage block matrices
2) MatrixBlockView to provide an practical interface for block matrices edition

The MatrixBlockUtils.*pp files contain functions related to block matrices edition
Update of the interfaces of the classes to match the new version of EpetraPreconditioner
1) Removing some errors
2) Renaming some variables
Implementation of the copyBlock function
Implementation of the createIdentityBlock function
Implementation of the createDiagBlock function
Implementation of the createUpperTriangularBlock function
Implementation of the createLowerTriangularBlock function
Implementation of the createLumpedBlock function
Implementation of the createInvLumpedBlock function
Update: copyBlock now works in parallel
Update: createIdentityBlock now works in parallel
Update: createDiagBlock now works in parallel
Update: createInvDiagBlock now works in parallel
Update: createUpperTriangularBlock now works in parallel
Update: createLowerTriangularBlock now works in parallel
Update: createLumpedBlock now works in parallel
Update: createInvLumpedBlock now works in parallel