Fix editing saving dhcp6prefixonly state

Reported in redmine #3097 and forum http://forum.pfsense.org/index.php/topic,64483.msg350255.html#msg350255
Merge pull request #716 from phil-davis/master

Fix editing saving dhcp6prefixonly state
When adding Port or URL alias default the alias type

When viewing the Port or URL aliases tab, and pressing "+" (add), make the default alias type match the Port or URL tab from which the user pressed "+".
Merge pull request #717 from phil-davis/master

When adding Port or URL alias default the alias type