space detection from translations in TJ operator arguments

[metebalci]

One way of adding space to text is (rather than using space characters) using translation values in the argument of TJ. In the example pdf (cli_tests/why_does_social.pdf), there are no space characters used and all spaces are given by translations. This can be used (e.g. by comparing to translation due to space character) to find out the word boundaries. --translation-heuristic option is added for this purpose but it is not working 100% correct yet and it can also be harmful in other cases.