Modify of tokenizer file position.
Optimization of work with position in Tokenizer.

- use inner class for representing Tokenizer::Position
- add methods for get and set position
Add speed test of tokenizer.
Small optimizations in Tokenizer.
Hints to tokenizer speed test.
Modification of tokenizer speed test.

- use bigger test file
- simplification of check of values
Modification of Tokenizer::Position.

- use struct for representation of Position
- simplification of using
Fix EOF problem in Tokenizer::set_position.

- add call clear method
- add problem to unit test
Merge branch 'DF_multifield' into DF_reader_management