Improvements to the installation process

This pull request makes a few improvements to the installation process.

The first commit puts the focus on the first field at each step of the installation.
It's nothing but it allows you to use only the keyboard during the installation (which is great when you make it twice because you forgot to switch to the *next* branch :smile:).

The second commit just adds a link on the url to the hackademic website at the end of the installation.

The last commit makes a few corrections on the *Navigation* menu on the right during the installation. The current step should be in a special color but it's not the case when you're at the end of the *database* step. Also, the colors for the two last steps are inverted.

Please tell me if there is anything to change or to explain.