Added the initial support for the database protection with the setuid
mechanism. In the beginning the program creates(or opens) the database
as a special user, and then switches to the real uid and functions
normally.
Creating files grants permanent permissions to them now. This makes
sense because if a program creates a new file, then it clearly can't
steal any data. This is particularly useful for programs which open an
obscene amount of auxilary files (e.g. neovim with a huge amount of
plugins).
Finally implemented the permanent permission tables using sqlite3. For
now, performance wasn't a consideration. There are a lot of
optimizations that could be made, like having prepared queries. The code
remains fairly untested.
Now the user can choose the "Allow this time." option when prompted.
`ask_access` will return 2 if this option is selected. So far, only the
GUI for this feature is implemented.
Now the program is completely functional and is using zenity dialogues.
`sources` directory was renamed to `src`. UI related stuff was moved to
`src/gui/ui`.
