made a callback option for entities, delete and save operations always occur in transactional state, still need to implement the callback for queries/find operations
Simplified params a callback can have. Extended the context interface and made it public, added some test, refactored all internal fetch,save and delete functions to use the current context, no more sqlCommon pointer to db needed
Merge branch 'development' of https://github.com/mbict/storm into development