Navigator: Tried to get error markers working; not there yet.

Will abandon for the moment - on the grounds that parsing from .asy might
be a more useful thing to do.
utils: Some small changes preparing for s-expression additions.
utils: Implement a small s-expression library.  Reads, writes, looks
vaugely like lisp, that kind of thing.
removed eclipse error filter (not needed)
SExpressions: Rename Type to SxType.. there's too many types floating around.
SExpressions: Add conversion to List (not 100% complete, but covers enough)
utils: Add a List printer
SExpression: Beef up reader so it works (at least mostly) on .asy files.
aldor.language: Add a first pass at an Aldor type model.

As it stands, this will read in .asy files and be able to answer questions
about type exports and parameters.

Design is pretty similar to the aldor compiler - differences are mostly
because java is a somewhat different language.

Anyway, idea of this (as well as being handy in eclipse), is that it can
serve as a model re-implementation in other languages (eg. Aldor).
SExpressions: Add ability to read escaped symbols.
SExpressions: Change SxType from an enum to a class to allow safe(ish) casting
instead of lots of unimplemented functions.
Types:
 - Introduce AbSyn --> Type conversion
 - Introduce type (and absyn) equality operations
 - Add srcpos attribute
 - Add effectiveValue to SymbolMeaning

Type equality isn't exactly correct, but enough to match a typical export
with its implementation.