AdminUI - Standardize button styles/labels

[colemanw]

Overview

Cleans up a few button styles in the Admin UI to be more consistent.

[civibot]

(Standard links)

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[larssandergreen]

These all look good, except I think we do need the Links text for Contribution Pages, otherwise it's kind of confusing because that hamburger menu is generally used for the View / Edit / etc links so I think users would expect those links underneath that menu.

[colemanw]

Ok @larssandergreen I've reverted that label.