Expand arp_responder help text

Add additional text to arp_responder help to ensure that
proper documentation is included in the configuration guide.

Make ML2 and L2population references consistent.

Closes-Bug: #1321320

Change-Id: I0fc0691fc3729aa39888c90ca871ad7f711343f8
corrects the typos in l3_router_plugin's comments

there were some typos in the docstring of the function
create_floatingip(). This patch corrects them

Change-Id: I869567d5470a27ff037feeabfc1057b8e2da38b7
Closes-Bug: #1359113
Merge "Expand arp_responder help text"
Merge "corrects the typos in l3_router_plugin's comments"