When adding Port or URL alias default the alias type (2.1 version)

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 "+".
This is a version for the 2.1 branch.
Merge pull request #719 from phil-davis/RELENG_2_1

When adding Port or URL alias default the alias type (2.1 version)