add possibility of calculating how many rows there were before LIMIT was applied

The Finder has get_rows_counter() method which returns how many rows there were
before LIMIT clause was applied. The select(...) method should be called with
Select::with_rows_counter flag in such a case.

while here:
- change the semantic of Finder, now the select(...) method takes a morm::Select flags,
  and we have such flags:
  - Select::no_auto_generated_columns - do not generate columns from models
  - with_rows_counter - add an additional column for the rows counter
- remove Finder::prepare_to_select() - now use select(...) with no_auto_generated_columns flag

src/model.cpp

@@ -934,6 +934,7 @@ void Model::map_values_from_query()
 		model_env->was_primary_key_read = false; // whether or not there was at least one column with primary_key flag
 		model_env->has_primary_key_set = true;   // whether all primary_columns were different than null
 		fields();
+		map_additional_columns_from_query();
 		model_env->model_work_mode = MORM_MODEL_WORK_MODE_NONE;
 
 		if( model_env->was_primary_key_read && model_env->has_primary_key_set )
@@ -950,6 +951,40 @@ void Model::map_values_from_query()
 }
 
 
+void Model::map_additional_columns_from_query()
+{
+	if( model_env )
+	{
+		if( model_env->select_flags.is_with_rows_counter() )
+		{
+			map_rows_counter_from_query();
+		}
+	}
+}
+
+
+void Model::map_rows_counter_from_query()
+{
+	if( model_env && model_env->cursor_helper )
+	{
+		/*
+		 * take the value only from the first row, the value should be the same on every row
+		 */
+		if( model_env->cursor_helper->current_row == 0 )
+		{
+			field(model_env->rows_counter_column_name.c_str(), L"", model_env->rows_counter);
+		}
+		else
+		{
+			if( model_env->cursor_helper && model_env->cursor_helper->has_autogenerated_select )
+			{
+				model_env->cursor_helper->current_column += 1;
+			}
+		}
+	}
+}
+
+
 
 void Model::clear()
 {