[jdom-interest] Processing instruction map issues

[Jason Hunter]

> If you have getters, it seems to make sense to have setters/adders.  I'm
> OK with addPseudoAttribute().  So then should it get
> getPseudoAttribute()?  Guess so.

I actually went with setPseudoAttribute() to match
Element.setAttribute() and be more clear that setting a new value for a
name overrides the original.  The behavior right now concerning setting
a map-style value to a PI with a non-map value is unchanged: it fully
replaces the old value.  I added a note in setPseudoAttribute() docs
about this.  It's not great, but I don't see the great solution.

-jh-