src folder and makefile improvements

makefile

@@ -13,7 +13,7 @@ testobjects= build/globals.o build/utils.o build/shuffle.o build/maths_functions
 evaluation_objects= build/globals.o build/utils.o build/shuffle.o build/maths_functions.o build/mpl_module.o build/gpl_module.o build/eval.o
 
 # rules to make object files into /build
-build/%.o: %.f90
+build/%.o: src/%.f90
 		@echo "F90 $@"
 		@$(FC) $(FFLAGS) -c $< -J build -o $@
 
@@ -26,6 +26,5 @@ test: $(testobjects)
 		@$(LD) -o $@ $^ $(LFLAGS)
 
 clean:
-		@rm -f *.o *.mod 
 		@rm -f build/*
 		@rm -f test eval