Fix OPENDJ-482: Validation for the CertificateSyntax
A huge thanks to Manuel Gaupp for this contribution.
In addition to the original contributed change I have made the following alterations:
* make the CertificateSyntax strictness configurable. By default the syntax will enforce the syntax, but this can be disabled if needed
* add a new method "isHumanReadable" to AttributeSyntax and AttributeType classes in order to make it easier to determine whether or not a syntax/type is human readable. This can be used in order to determine whether or not an attribute value can be included in log messages, for example.