Add interface, trait, and const templates

[MikkelPaulson]

I've moved interfaces into their own template/regex to change:

/**
 * Class: baz
 *
 * @see foo
 */
interface baz extends foo, bar { }

Into:

/**
 * Interface: baz
 *
 * @see foo
 * @see bar
 */
interface baz extends foo, bar { }

And I've added support for traits, which was missing. The regex for that one is nice and simple. :)

[tobyS]

Sorry for the delay.