makefiles: add code generator targets

These targets will bootstrap code for an example application, a test application or a new board support. The 'riotgen' tool is used behind

Makefile

@@ -43,4 +43,5 @@ print-versions:
 include makefiles/boards.inc.mk
 include makefiles/app_dirs.inc.mk
 
+include makefiles/tools/riotgen.inc.mk
 -include makefiles/tests.inc.mk

makefiles/tools/riotgen.inc.mk

@@ -0,0 +1,17 @@
+.PHONY: riotgen-installed generate-%
+
+-include makefiles/color.inc.mk
+
+riotgen-installed:
+	@command -v riotgen 2>&1 > /dev/null || \
+	{ $(COLOR_ECHO) \
+	"$(COLOR_RED)'riotgen' command is not available \
+	please consider installing it from \
+	https://pypi.python.org/pypi/riotgen$(COLOR_RESET)"; \
+	exit 1; }
+
+GENERATORS = board driver example module pkg test
+$(addprefix generate-,$(GENERATORS)): generate-%
+
+generate-%: riotgen-installed
+	@RIOTBASE=$(CURDIR) riotgen $* -i