[Grace-core] Layout rules for Grace

[James Noble]

> Herewith is a first cut at layout rules for Grace.  

great - although I wonder if this (or at least the next iterations)
would go better on the Wiki (or svn?) than very many emails.

> 
> • The : that introduces a type annotation shall not have spaces before or after
> 	Example:     speed:aNumber

so far, I've almost always done the direct opposite:  "speed : Number" 

one variant I'm not that keen on is the Scala style "speed: Number"
perhaps because it looks too much like Smalltalk (but means something very different)
and because, well, as David Pearce has said, why not then just follow Go "speed Number"
and omit the colon?

James