separated API multiplications from operations

in order to shrink the bloated set of operations, making those remaining "standard" and trace-preserving (with the exception of the applyQubitProjector and applyMultiQubitProjector). The new multiplications module is catered to "raw" linear algebra upon density matrices

Author: TysonRayJones

quest/include/multiplication.h

@@ -50,6 +50,7 @@
 #include "quest/include/environment.h"
 #include "quest/include/initialisations.h"
 #include "quest/include/channels.h"
+#include "quest/include/multiplication.h"
 #include "quest/include/operations.h"
 #include "quest/include/paulis.h"
 #include "quest/include/qureg.h"

quest/include/operations.h

@@ -8,6 +8,7 @@ target_sources(QuEST
   initialisations.cpp
   matrices.cpp
   modes.cpp
+  multiplication.cpp
   operations.cpp
   paulis.cpp
   qureg.cpp