Test container type is added.

Test container is planned to test codezero microkernel extensively.
With these changes, everything is there to develop a full-featured test suite.
It also exemplifies how a new container type can be added to the system.
(cherry picked from commit f21fa53df421bfc8eeeaa096c89b98beed436c60)

conts/test/main.c

@@ -0,0 +1,16 @@
+/*
+ * Main function for this container
+ */
+#include <l4lib/arch/syslib.h>
+#include <l4lib/arch/syscalls.h>
+#include <l4/api/space.h>
+
+extern int print_hello_world(void);
+
+int main(void)
+{
+	print_hello_world();
+
+	return 0;
+}
+