Create Strong Typed Interfaces for DAOs

[Danielku15]

There are no strong typed interfaces defined for all DAOs which need to exist. The IDaoFactory simply enforces to return any object. Please add clear interfaces which define the methods a DAO should implement:

interface IActivityDao extends IDao<Activity> {}
interface IConfigurationDao extends IDao<Configuration>  {} 
...

And implement the interfaces on the current Daos:

class Db4oActivityDao extends Db4oDaoBase<Activity> implements IActivityDao {}