Big update
- appendRow() also inserts null values into fields not defined by the $values-parameter
- getRow() handles negative parameter values
- AOOSMODEL_PROP_UNIQUE and AOOSMODEL_PROP_DATA_INCREASING implemented
- In order to implement above, _fixDataProps was changed a bit
- AOOSMODEL_PROP_DATA_DECREASING removed
- drop() was added.
- remove() was fixed - didn't remove rows after AOOSModelRow was added
- populate() was fixed - didn't check properly for select errors
- AOOSModelRow is now constructed with a column index