[Grace-core] Type checking dialect

[James Noble]

> It's in the sample/dialects directory if you pull the latest changes from Michael's repository.

yep, just done a "git pull" and got:

 sample/dialects/checking.grace               |  525 ++++++++++++
 sample/dialects/structural.grace             | 1130 ++++++++++++++++++++++++++

> You'll probably have to move them down into the root compiler directory to get it to run. Once the latest changes are available you'll be able to run it from the JS backend.
> 
>> I'm not quite sure what "this" is bound to.
> 
> The testing. I'm prioritising working on introducing this in the paper.

yes that's the right approach

James