Define a target count for session/the whole document

The idea here is that the user can define the number of symbols/words/lines/paragraphs/pages (based on his formula) that he must accomplish. And then, the status bar will display the percentage or simply the number of units already written/total amount of units needed. That is really useful for students, that often have to write essays (say, 400 words or less, etc.) or journalists who have to deal with their magazine's limitation (for example, 20000 symbols or less).