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
