RDFa parse issue if vocab not defined with training slash

[davidcockbill]

Originally raised against ANY23: ANY23-428

If a RDFa vocab URL is missing a trailing forward slash, then properties and types are not expanded correctly.
For example:

<ol vocab="https://schema.org" typeof="BreadcrumbList">

rather than:

<ol vocab="https://schema.org/" typeof="BreadcrumbList">

produces properties and types that look as follows:

<http://schema.orgBreadcrumbList> .

The fix, I believe, needs to be in "rdfa/src/main/java/org/semarglproject/rdf/rdfa/Vocabulary.java".
I changed the resolveTerm() method as follows:

  String resolveTerm(final String term) {
   	final String separator = (url.endsWith("/") || url.endsWith("#")) ? "" : "/";
       final String termUri = url + separator + term;
       if (terms == null && RIUtils.isAbsoluteIri(termUri) || terms != null && terms.contains(termUri)) {
           return termUri;
       }
       return null;
   }

This seems to fix the issue; and the semarglproject unit tests pass. However, I'm not too sure if there are other issues with this, and whether we should use a URI library for creating the url rather than my crude string parsing.