Adding starter code and solution for p4runtime exercise (#81)

Summary of changes:
- Adding the p4runtime starter code and solution.
- Adding NO_P4, BMV2_SWITCH_EXE and P4C_ARGS to utils/Makefile
- Updated p4runtime/Makefile to use variables
- Adding conversion functions for match and action param values
- Separating P4Info and P4Runtime libraries
- Updating global README and adding p4runtime/README.md
- Disabling screen saver on VM GUI
- Adding desktop icons for Terminal, Wireshare and Sublime Text
- Updating topo.pdf -> png for Markdown viewing in basic_tunnel and
  p4runtime READMEs

P4D2_2017_Fall/utils/Makefile

@@ -11,10 +11,20 @@ outfile := $(source:.p4=.json)
 
 compiled_json := $(BUILD_DIR)/$(outfile)
 
+# Define NO_P4 to start BMv2 without a program
+ifndef NO_P4
+run_args += -j $(compiled_json)
+endif
+
+# Set BMV2_SWITCH_EXE to override the BMv2 target
+ifdef BMV2_SWITCH_EXE
+run_args += -b $(BMV2_SWITCH_EXE)
+endif
+
 all: run
 
-run: build 
-	sudo python $(RUN_SCRIPT) -t $(TOPO) -j $(compiled_json)
+run: build
+	sudo python $(RUN_SCRIPT) -t $(TOPO) $(run_args)
 
 stop:
 	sudo mn -c
@@ -22,7 +32,7 @@ stop:
 build: dirs $(compiled_json)
 
 $(BUILD_DIR)/%.json: %.p4
-	$(P4C) --p4v 16 -o $@ $<
+	$(P4C) --p4v 16 $(P4C_ARGS) -o $@ $<
 
 dirs:
 	mkdir -p $(BUILD_DIR) $(PCAP_DIR) $(LOG_DIR)