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/exercises/p4runtime/Makefile

@@ -1,10 +1,5 @@
+BMV2_SWITCH_EXE = simple_switch_grpc
+NO_P4 = true
+P4C_ARGS = --p4runtime-file $(basename $@).p4info --p4runtime-format text
+
 include ../../utils/Makefile
-
-# Override build method to use simple_switch_grpc target
-run: build
-	sudo python $(RUN_SCRIPT) -t $(TOPO) -b simple_switch_grpc
-
-# Override p4c step to also produce p4info file
-P4INFO_ARGS = --p4runtime-file $(basename $@).p4info --p4runtime-format text
-$(BUILD_DIR)/%.json: %.p4
-	$(P4C) --p4v 16 $(P4INFO_ARGS) -o $@ $<