Added tests for AbstractFilter::__construct
Added tests for AbstractFilter::isEmpty
Added tests for AbstractFilter::getSearchMethods
AbstractFilter::getSearchMethods should return the methods of the child class, not the abstract one
Added tests for AbstractFilter::exact
Reverted changes for AbstractFilter::getSearchMethods
Added tests for AbstractFilter::getFieldName
Added tests for AbstractFilter::search
Added tests for AbstractFilter::getFieldType
Updated AbstractFilter::getFieldType to support column types formed by multiple words