Create Datastore classes from the model

[ondrej-kvasnovsky]

• write tests
• create data store

[tomasvantuch]

data store created, tests too...
...there was implemented just fundamental methods to each entity as put(insert/update), delete(delete), get/getBy(select)...test methods are for all (mostly) methods and work well, for now...
...I didn't use ContextInitializer, by the tutorial I used registration of all entitties on one place - DaoFactoryObjectify
...please check DaoUserObjectify method getByName...here there is needed to be implemented with using LIKE operator but I din'd find how could it be...that horrible operations are there for supporting equal values and null values...