Expression parser working, rings and kinds still buggy
Added more declaration support, rings not working
Updated exp.mli and .ml, still hainvg errors parsing rings
Solved ring parsing problem, added adjacency for multiply
Changed grammar of adjacency
added support for rigid variables

but fully ready, yet. Users constants will clash with typer's
removed clashing with user constants.
Dim got his own new flat, i.e. a module.
abstracted nat1

and inversed dependencies between Nat1 and Ast.
removed all warnings

and fixed some bugs occasionally.
typer now accepts parser's output.
fixed a bug in a typer and added some more tests.
added ulex
removed exp helpers functions from exp module and moved them directly to parser.