Fixed line and offset number reporting.  Exposed validation detail string so it can be reused by raml-to-jaxrs generator

I considered putting the toDetailedString() method in the raml-to-jaxrs generator only, but decided that it should be in parser so the same code will be used by both the parser and the raml-to-jaxrs generator.   I also fixed printing of line and column numbers as they were previously 0-offset rather than 1-offset.