Optimize ShEx for EXTRA predicates with non-repeated properties

[labra]

A common pattern for Shape expressions is:

<S> EXTRA <p> {
 <p> @<T> {min,max}, 
 ... // other definitions without mentioning <p>
}

The meaning is that we expect between min and max values of property <p> with shape <T> and we don't give any further constraint on the rest of values of property <p>.

Currently, this pattern is checked using a regular expression like: C0{min,max}, C1* where C0 represents the <p> @<T> constraint and C1 represents the <p> NOT @<T> constraint which is very inefficient and can raise stack overflow exceptions as in issue #130

An optimization to validate shapes following this pattern is to count the number of values with property <p> that conform to shape <T> and check that it is between min and max.

[labra]

The optimization has been implemented and tested. Further optimizations can be done but will have their own issues.