Allow select column width for widget cards

[decabeza]

References

Add cards to custom pages #3149

Background

Admins can create cards for homepage on /admin/widget/cards/new and since #3149 also for custom pages on /admin/widget/cards/new?page_id=N.

Objectives

• Add columns to widget cards: this add a select on each card new form to select the number of columns for their width (for a better UX on mobile screens it's always 100%)
• Improve notice message for pages cards.
• Improve CSS layout.
• Show card label only if it is present: until now was showing an empty span.
• Remove unnecessary title on page cards: on custom pages a "Featured title" is not necessary.
• Add columns on welcome card view: I include this feature for the cards created for the homepage.
• Fix hound warnings. Clean code! ✊🤓

Notes

For cards you can use from 1 to 12 columns, based on [Foundation Float Grid].(https://foundation.zurb.com/sites/docs/grid.html)

Visual Changes

New select on admin card new form

Now you can create more interesting layouts

BEFORE if a card didn't have a label show a blank span

Now show card label only if it is present

You can use from 1 to 12 columns