Add Project Identifier variable and target

* A variable (IDENTIFIER) was added to allow the 'identifier' target to
  search source code and header files for a matching hash parametrically.
* The phony 'identifier' target greps for the IDENTIFIER pattern in each file
  and fails if any source/header doesn't contain the pattern.
* The identifier target is added as a dependency to fullsubmit and
  partialsubmit.
* Editing IDENTIFIER is now part of the first student TODO in the Makefile.

Makefile

@@ -20,12 +20,16 @@
 #######################
 # TODO (begin) #
 #######################
+# Change IDENTIFIER to match the project identifier given in the project spec.
+IDENTIFIER = EEC50281EEC50281EEC50281EEC50281EEC50281
+
 # Change EXECUTABLE to match the command name given in the project spec.
 EXECUTABLE  = executable
 DEBUG       = $(EXECUTABLE)_debug
 
-# If main() is in a file named project*.cpp, use the following line
-PROJECTFILE = $(or $(wildcard project*.cpp), $(EXECUTABLE).cpp)
+# The following line looks for a project's main() in a file named project*.cpp,
+# executable.cpp (substituted from EXECUTABLE above), or main.cpp
+PROJECTFILE = $(or $(wildcard project*.cpp), $(wildcard $(EXECUTABLE).cpp), main.cpp)
 # If main() is in another file delete line above, edit and uncomment below
 #PROJECTFILE = mymainfile.cpp
 #######################
@@ -88,6 +92,11 @@ static:
 	cppcheck --enable=all --suppress=missingIncludeSystem \
       $(SOURCES) *.h *.hpp
 
+# make identifier - will ensure that all source code and header files include
+#                   the project identifier
+identifier:
+	@if [ $$(grep --include=*.{h,hpp,c,cpp} -L $(IDENTIFIER) * | wc -l) -ne 0 ]; then echo "Missing project identifier"; exit 1; fi
+
 # Build both release and debug executables
 all: clean
 	$(MAKE) -Rr release
@@ -151,8 +160,8 @@ $(FULL_SUBMITFILE): $(FULL_SUBMITFILES)
 	@echo !!! Final submission prepared, test cases included... READY FOR GRADING !!!
 
 # shortcut for make submit tarballs
-partialsubmit: $(PARTIAL_SUBMITFILE)
-fullsubmit: $(FULL_SUBMITFILE)
+partialsubmit: identifier $(PARTIAL_SUBMITFILE)
+fullsubmit: identifier $(FULL_SUBMITFILE)
 
 sync2caen: REMOTE_PATH := ${REMOTE_BASEDIR}/$(notdir $(shell pwd))
 sync2caen:
@@ -257,6 +266,6 @@ help:
 
 # these targets do not create any files
 .PHONY: all release debug profile static clean alltests partialsubmit \
-        fullsubmit sync2caen help
+        fullsubmit sync2caen help identifier
 # disable built-in rules
 .SUFFIXES: