Changes to get orient-spring-tx working for orientdb 2.0

I have done some work to get it working with orientdb 2.0. 

Can you please check if the work looks ok? 

I guess you probably do not want to merge this, but perhaps create a branch so a 2.0 version of this library can be released and make a final 0.3.0 version for pre 2.0 orientdb versions.