NitSig: Sigarra, but Neater

NitSig improves SIGARRA's user experience by simplifying and decluttering its UI. Notable features include:
- A brand new navigation top bar
- A more readable font
- Better student and teacher profiles
- Collapsible sections in class unit pages
- Improved user experience in schedules
- Auto login, so you don't have to enter your credentials every time
- And many more little improvements!

Note* NitSig only works for FEUP's SIGARRA, but support for other faculties is planned.