[nem-en] Manager class

[Mark Haniford]

Since the code completion engine has come up for discussion, I was
curious if the completion engine can do incremental parsing?   I'm not
a compiler guy, but what I've seen of the example at the website, it
parses a whole file/buffer.  It seems that for completion you need to
feed the parser stuff as the user types/copy-n-pastes, etc..  Do you
maybe have to use some parts of the nemerle.compiler library outside
of the scope of the completion engine?