Allow to show the current progress in the window titlebar

[sergio-costas]

When building a snap with several parts using -v, it's usually not possible to know which part is being built due to the long text output. An idea (with a much-to-be-desired proposal here: canonical/snapcraft#4217 ) would be to allow to show the progress text in the window titlebar, by using the ANSI codes for that.

A proposal would be to add a new boolean named parameter to the progress method, that, when set to True, will not only show the string in the screen, but also set it as the window title.

These are some ideas for that named parameter:

• update_titlebar
• set_titlebar
• set_on_titlebar
• titlebar
• on_titlebar
• copy_on_titlebar
• dup_on_titlebar

[sergio-costas]

@tigarmo I made a proposal implementation in #160