fixed division by zero and few other bugs and enchanced whos online and staff online modules

Fixes for whos online and staff online modules.

- fixed division by zero bug and various other bugs within these 2
modules.
- added functionality where value of 0 for columns or rows set in
options panel will hide avatars and leave only text output.
- added text output to staff online module in case of disabling avatars.
- changed various language variables for these 2 modules.
- improved tip for modules in options panel
Merge pull request #13 from avril-gh/master

fix division by zero, avatars, ect