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

samples/Makefile.dep

@@ -22,9 +22,9 @@
 ./main.o: ../src/cursorhelper.h ../src/finderhelper.h
 ./main.o: ../src/fieldvaluehelper.h ../src/wrapper.h ../src/spacewrapper.h
 ./main.o: ../src/baseobjectwrapper.h ../src/modelcontainerwrapper.h
-./main.o: ../../pikotools/src/convert/text.h ../src/flatexpression.h
-./main.o: ../src/finder.h ../src/cursor.h ../src/jsonexpression.h
-./main.o: ../src/postgresqlexpression.h ../src/jsonconnector.h
-./main.o: ../src/postgresqlconnector.h ../src/postgresqlqueryresult.h
-./main.o: ../src/transaction.h person.h language.h attachment.h type.h
-./main.o: attachment2.h
+./main.o: ../src/select.h ../../pikotools/src/convert/text.h
+./main.o: ../src/flatexpression.h ../src/finder.h ../src/cursor.h
+./main.o: ../src/jsonexpression.h ../src/postgresqlexpression.h
+./main.o: ../src/jsonconnector.h ../src/postgresqlconnector.h
+./main.o: ../src/postgresqlqueryresult.h ../src/transaction.h person.h
+./main.o: language.h attachment.h type.h attachment2.h