Support for OR, AND and NOT expressions in UML visualizations

[labra]

At this moment, ShEx visualizations as UML diagrams don't support values which contain AND, OR or NOT. For example, the following schema:

prefix : <http://example.org/>
prefix xsd: <http://www.w3.org/2001/XMLSchema#>

:S {
  :s1 @:U OR @:U ;
  :s2 NOT @:U
}
:T {
  :t1 @:U OR @:V ;
  :t2 NOT @:V
}
:U {
  :u1 @:V AND @:V ;
  :u2 xsd:string OR xsd:integer
}
:V {
  :v1 xsd:integer OR @:S
}

At this moment, this schema is not possible to be visualized.