Added captcha generation. As we're working without JS - there is no
possibility to reload image, only if user will reload whole web page.
Some design works - set monospace font for paste textarea (will
use system-defined default monospace font) and lowered font size
in paste views.
Pagination now works. Temporary hardcoded 10 pastes per page, will be put
in configuration later. Maybe.
From now user will receive readable error message if error occured.
Started to work on syntax highlighting, tried to make lexers detection
work but apparently to no avail.
