Implements set_entry method

I have a task - create an entry in the module and relate it with the other entry. 
The problem is that the dynamic method set_enty returned dictionary, but method relate occure SugarEntry object. 

I changed the code, for convenience redefined the dynamic creation methods, api for easy overriding them. 
Created method set_entry, which works as before, only returns SugarEntry object instead dictionary, which can be used further.

Sorry for bad english!