Improve some plugins help strings
Improve some plugins help strings

For consistency add a "." everywhere, remove an extra space at end of a
string, add missing space between strings, fix descriptions and
capitalization.

Change-Id: Ib1523352b19768425263c09855d6a218e06e588a

openstack/networking-nec,openstack/networking-nec,stackforge/networking-nec,stackforge/networking-nec