add to file outline

quad/doc/Makefiles.md

 #  How to use the makefiles
+## library.mk
+This contains many definitions of make targets
+//describe existing targets
 
+## executable.mk
+//describe targets
 
+## quad/Makefile
+// describe what is here
 
+## Low level Makefile
+Each library needs its own Makefile.
+//Give contents of the makefiles
+
+## How to add a library
+//how would you add a library?