Add interface for PETSc vector

@TomFischer @norihiro-w @endJunction @bilke : The previous pull request about the PETSc interface has been split into four. This is the second part: an interface for PETSc vector.

Add class InforMPI in BaseLib/MPI, and changed the corresponding CMakeLists.txt

Add test for the number of processors in usage. 

Changes according to the comments by Nori and Dima

Rewrite  collectLocalVectors. Some other changes according to Nori's comments. Put calling  MPI_Comm_rank local according to a test results on EVE.
1000,000 times calling:  0.02 s
1000,000,000 times calling: 10.77 s
@norihiro-w