Add SerialVectorMatrixBuilder test.

It is checking only creation and sizes of the vector and matrix.
Add SerialExecutor test for std::vector.
Remove unused vector and matrix assemblers.
Move LinearSystemAssembler and its test to AssemblerLib.

Cleaning up the files and corresponding directories as well as cmake inputs.
Rename files in Tests/AssemblerLib.
Remove serialExecute() overload for iterators.
Replace delegating ctor in LocalToGlobalIndexMap.
Replace delegating ctor in GlobalDenseMatrix.
Add explicit specifier to LocalToGlobalIndexMap(rows) ctor.
Compose vector/matrix builder in GlobalSetup structure.

Also add a typical setup using GlobalDense matrix and SerialExecutor.