Fix cross-document references to 'playbooks' in the modules source.

Update manpages from ansible repo to show when options require args.

Update clean target Makefile so 'rm' doesn't print a useless error
when files aren't found while cleaning.

Makefile

@@ -19,8 +19,8 @@ htmldocs:
 	 ./build-site.py rst
 
 clean:
-	-rm .buildinfo
-	-rm *.inv
+	-rm -f .buildinfo
+	-rm -f *.inv
 	-rm -rf *.doctrees
 	@echo "Cleaning up byte compiled python stuff"
 	find . -regex ".*\.py[co]$$" -delete