PR: Make status bar widgets to have a fixed width

[mariacamilarg]

Fixes #2238

[ccordoba12]

Could you post screenshots of before and after this change?

[mariacamilarg]

@ccordoba12 Sure:

I don't know if it is easy to see, but the widths of the labels are fixed no matter the number. It was kinda tricky taking the screenshots but the width in both is the same.

[ccordoba12]

Looks good to me. @goanpeca, do you agree?

[goanpeca]

Yes and no, I think what we should aim for is to have widgets aligned to the right as well, so not only setting a fixed width (a bit arbitrarily at the moment), but also using strecthes in the Layout definition.

So for example between the CPU text and the 29% there should be a stretch so that the widget move to the right, so they are right aligned.

[goanpeca]

So that the widget looks like

CPU     15%
CPU      5%

and not

CPU     15%
CPU     5%

I exaggerated the space so that you get the idea :-p