Fixed a bug where root nodes couldn't look at their own internals.

Seeing if a node matched itself took place at the same time that
siblings were being checked, but of course root nodes have no siblings
so that whole step got skipped.
Removed "compile as library" distinction for compiling

Now each PLEXIL file created can be used either as a root or as a
library node, just like in regular PLEXIL (although of course a PLEXIL
plan is usually meant to be one or the other).