Set the terminal title to gitui ({repo_path})

[acuteenvy]

This Pull Request fixes/closes #2462.

It changes the following:

• Always set the terminal title to gitui ({repo_path}).
  It looks like this:
  

I followed the checklist:

• I added unittests
• I ran make check without errors
• I tested the overall application
• I added an appropriate item to the changelog

[cruessler]

I tested this in Alacritty and the window title reflected the directory I had run cargo run in.

[extrawurst]

@acuteenvy would you mind updating your branch to make it mergable?

[extrawurst]

Awesome! Thanks!

[savchenko]

This is great, but can it be made optional?