Various improvements and refactorings of the admin framework client API, including:
* client API methods are much more specific about what sort of exceptions they can throw
* new exceptions for wrapping underlying transport related error conditions (e.g. IO problems, authorization problems)
* improved Javadoc generation for client APIs
* pull-up AbstractPropertyDefinitionVisitor into PropertyDefinitionVisitor and improve type-safety of EnumPropertyDefinition visitor method
* refactor the LDAP client implementation (remove LDAPChangeBuilder, introduce JNDI DirContext wrapper interface called LDAPConnection to make the client APIs more testable)
* move various unit test classes out of the admin server-side unit tests so that they can be re-used by client unit tests
* introduce "mock" client connections and property providers to facilitate testing of the admin client API
* implement client API unit tests
