making interactive mode more user-friendly.

users can now execute an expression, define functions, etc
in interactive mode without explicitly sending an EOF signal.
Ctrl+D now explicitly exits interactive Luci.

also changed the definition of a function call in the parser
to be only and ID ( expr ) or CGET ( expr ). I thought this
caused shift/reduce conflicts before, but it's indeed correct
and Bison doesn't complain.
updating project documentation

the documentation is semi-dependent on Github Flavored Markdown,
particularly with respect to newlines and relative links.
it should look good online though.
some more docs and experimenting with exceptions.