Remove line spacing when reading lines

Signed-off-by: Igor Popov <igor.popov89@gmail.com>
Extract method for reading lines

Signed-off-by: Igor Popov <igor.popov89@gmail.com>
Rename constant to SYMBOL_HEIGHT

Signed-off-by: Igor Popov <igor.popov89@gmail.com>
Add constant for line spacing

Signed-off-by: Igor Popov <igor.popov89@gmail.com>
Add canExtractOneSymbolFromLine test for SymbolExtractor

Signed-off-by: Igor Popov <igor.popov89@gmail.com>