[Dash] Centered title should be requested by scopes explicitly and limited to one line

[Alejandro J. Cura]

When showing overlays, the title is always centered and the attributes and subtitles are left-aligned, so it looks wrong.
This screenshot shows the issue: https://launchpadlibrarian.net/183466031/scopes-less-attrs.png

Saviq's suggestion to fix this is to make titles always left aligned too, and to extend the category renderer so some scopes can align to the center if needed, using something like this:
 { "title" : { "field": "title", "align": "center"}, ...}

All categories that wish to have centered titles need to send the above in components, otherwise will be left-aligned.

NOTE also that this will force just a single line of title, so anything that doesn't fit in one line will be elided.

This is all according to the spec:
https://sites.google.com/a/canonical.com/unity8dash/toolkit/4-cards#TOC-Header-Text-Styles

[UX Comment]
As suggested by Alejandro "With the latest changes to the spec and the unity8 branch there's no need for further changes in the scopes, so I'm marking the click scope as invalid for this bug."

[Michał Sawicz (saviq)]

Remote scopes - Wikipedia is affected.

[Michał Sawicz (saviq)]

Looking through the apps scope, enforcing the single-line element of this might be a problem, there's a lot of apps whose names won't fit in a single line (especially translated).

Adding ubuntu-ux for design feedback.

[Alejandro J. Cura (alecu)]

I think the spec is wrong where it says that only one line should be shown, because in the scope that shows installed apps there are quite a few that need more than one line of title in English (eg: Dropping Letters, System Settings), and there will be more in other languages too.

[Facundo Batista (facundo)]

This issue doesn't affect the Ubuntu Rest Scopes project, logo overlays are not used there.

[Alejandro J. Cura (alecu)]

With the latest changes to the spec and the unity8 branch there's no need for further changes in the scopes, so I'm marking the click scope as invalid for this bug.