Split SerialVectorMatrixBuilder into Dense and Lis variants.
Move SerialVectorMatrixBuilder into AssemblerLib.
Correct global assembler operator() constness.
Extract AssemblerLib::SerialExecutor from vector/matrix builder.

Both are independent of each other.
Remove element type from serialExecute. Add iterator version.
Invert argument order in serialExecute().
Make SerialVectorMatrixBuilder create functions static.
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.
Add static specifier to all GlobalSetup member functions.
Uncrustify TestSerialLinearSolver. Replace tabs with spaces.
Rename LinearSystemAssembler to VectorMatrixAssembler.

This reflects that this class can be used otherwise as only for
linear equation system assembly.