Throw UnsupportedOperationException from unimplemented Neo4jStatement methods

Fix for #17. Neo4jStatement should not fail silently when methods are called which are currently not supported.

I've added code that throws UOE from every method where it was obvious to me. There some methods I'm not sure about:
* execute(String, int)
* execute(String, int[])
* execute(String, String[])
* executeUpdate(String)
* executeUpdate(String, int)
* executeUpdate(String, int[])
* executeUpdate(String, String[])
* isWrapperFor(Class<?>)
* getMoreResults()
* getMoreResults(int)
* unwrap(Class<T>)

These methods contain logic, but they don't look correct to me. For example all the execute methods delegate to execute(String) and ignore any additional parameters.
I don't know for sure, but [this discussion](http://stackoverflow.com/questions/295920/how-can-i-abort-a-running-jdbc-transaction) indicates that only the statement is canceled. ```Connection.rollback()``` has to be called explicitly after a statement has been canceled.