added filter on model objects
Merge pull request #2 from r00tl3ss/query_filter

added filter on model objects
Tested merged method
Now exclude can be called on objects directly
Added chaining capability
Tested direct exclude on objects
Starting to implement other side for the foreign key
Implemented that you can get the other side of the foreign key
Tested if you can filter the other side of the foreign key
Added new version
Added simple method to get a model or create at least an instance of it
Testing get or create model
Added simple order by for models
Testing both sorting directions
Tested limiting in normal queries
Tested model limiting
New version with small updates