Various changes

There are several changes, most of them for the UI, and some bugs fixed too:
- The answer shown as the most voted is now working.
- Question creation has a hidden form that appears clicking on the button.
- There are help instructions clicking on the question mark on the index page.
- It is visually shown when a question is created.
- Some fonts were changed.
- Added default date for question creators

There is still work to do. I don't like how the tables look yet, when an empty form is submitted the errors appear in the wrong way, etc. But we are getting there... :)