Fix and get better fonts for gitk running on Ubuntu

You can make Gitk fonts look better! Gitk fonts are handled by the simple windowing shell (wish), it should be configured and the different graphical toolkit should be installed:

# Getting different graphical toolkit (tk8.5)
sudo apt-get install tk8.5
# Switching toolkit. Choose the /usr/bin/wish8.5 item
sudo update-alternatives --config wish

Enjoy gitk with the better front now!

You can always rollback these changes by performing the last step once again and choosing the first selection item.