Implement SHACL Compact Syntax

[gkellogg]

From the draft at https://w3c.github.io/shacl/shacl-compact-syntax/.

Example of compact syntax:

BASE <http://example.com/ns>

IMPORTS <http://example.com/person-ontology>

PREFIX ex: <http://example.com/ns#>

shape ex:PersonShape -> ex:Person {
	closed=true ignoredProperties=[rdf:type] . 

	ex:ssn       xsd:string [0..1] pattern="^\\d{3}-\\d{2}-\\d{4}$" .
	ex:worksFor  IRI ex:Company [0..*] .
	ex:address   BlankNode [0..1] {
		ex:city xsd:string [1..1] .
		ex:postalCode xsd:integer|xsd:string [1..1] maxLength=5 .
	} .
}