New component: cat

Generically reads an arbitrary file natively.

Saves a few layers of execution in comparison to using `run_command`
with an argument like `cat ./file`.

Makefile

@@ -7,6 +7,7 @@ include config.mk
 REQ = util
 COM =\
 	components/battery\
+	components/cat\
 	components/cpu\
 	components/datetime\
 	components/disk\