Change include management.

Now subdirectory must be specified. The main reason for this change, is that this explicitely sets where the file is. Moreover, it "simplifies" CMakeLists.txt files.

src/algebra/CRSMatrix.hpp

 #ifndef CRS_MATRIX_HPP
 #define CRS_MATRIX_HPP
 
-#include <Array.hpp>
 #include <Kokkos_StaticCrsGraph.hpp>
-#include <PugsAssert.hpp>
 
-#include <SparseMatrixDescriptor.hpp>
+#include <utils/Array.hpp>
+#include <utils/PugsAssert.hpp>
 
-#include <Vector.hpp>
+#include <algebra/SparseMatrixDescriptor.hpp>
+#include <algebra/Vector.hpp>
 
 #include <iostream>