Add counters to TCPFragmenter

This element now counts

	* count -- the total number of packets
	* fragmented_count -- the number of packets fragmented
	* fragments -- the number of fragments produced

Thanks to Cliff Frey for the suggestion.

Reviewed-By: cliff@meraki.com

git-svn-id: svn+ssh://svn.meraki.net/var/local/svnbase/meraki/trunk/router@102019 291e08f9-2c14-0410-acb0-c89b6de265c5