Stokhos:  Add MP::Vector PDE assembly performance test.

This is based off of Kokkos/FENL, and extracts just the assembly portion
of that example.  It compares an ensemble assembly with MP::Vector to a
standard serial loop over the ensemble.
Stokhos:  Add alignment attribute for StaticFixedStorage.

Ensures MP::Vector with StaticFixedStorage is aligned properly when
using Intel compilers.
Stokhos:  Add ivdep and unroll pragama's to MP::Vector

The ivdep pragma helps the Intel compiler vectorize through the
expression template assignment operators.  The unroll pragma is there
but currently disabled as it generally slows things down.  Also
optimized the performance of the +=, -=, *=, and /= operators.  Finally
added a (currently disabled) partial specialization of MP::Vector for
StaticFixedStorage that doesn't use expression templates.  The idea
behind this was to make vectorization easier, but it generally is
slower, I think because it prohibits FMA on MIC.
Stokhos:  Disable Serial version of KokkosArrayKernelsUnitTest.

After a recent commit by Christian, this one no longer compiles due to
some missing functionality in the Serial device.
Stokhos:  Fix MP::Vector {+=, -=, *=, /=} constant.
Stokhos:  Update MueLu instantiations for recent changes.

I had to add a placeholder for MueLu::Constraint as the default
implementation doesn't compile due to use of Teuchos::LAPACK.  Currently
I just provide a blank implementation for Stokhos to get things to
compile.  In the future I will have to address this.
Stokhos:  kokkoslinalg -> kokkoscorelinalg

Not really sure why I list this explicitly in DEPLIBS.
Stokhos:  Fix MPAssembly test vector import for Cuda without UVM.
Stokhos:  Fix printing of header for MPI.