Updated makefile to upgrade pip during venv setup.

After creating fresh virtual environment the 'pip' and 'wheel' packages inside this venv will be upgraded to latest versions. (Redmine issue: #3387)

Makefile

@@ -178,6 +178,11 @@ venv: FORCE
 		echo "$(CYAN)Virtual environment successfully created in '$(VENV_PATH)'.$(NC)";\
 	fi
 	@echo ""
+	@echo "Upgrading 'pip' and 'wheel' within the virtual environment to latest versions"
+	@echo ""
+	@$(VENV_PATH)/bin/pip install --upgrade pip
+	@$(VENV_PATH)/bin/pip install --upgrade wheel
+	@echo ""
 	@echo "Venv path: `. $(VENV_PATH)/bin/activate && python -c 'import sys; print(sys.prefix)'`"
 	@echo "Python stuff versions:"
 	@echo ""