Add action icons to object list views

Summary:
We have a few interfaces where add "Edit", "Delete" or some other action to a list. Currently, this happens via icons, but these are cumbersome and weird, are inconsistent, can't be workflow'd, are hard to hit on desktops and virtually impossible to hit on mobile, and generally just feel iffy to me. Prominent examples are Projects and Flags. I'd like to try adding an "edit" action to Maniphest (to provide quick edit from list views, basically). It looks like some of Releeph would benefit here, as well.

Instead, provide first-class actions:

{F42978}

They produce targets which my meaty ham-fists can plausibly hit on mobile, too:

{F42979}

(We could do some kind of swipe-to-expose thing eventually, but I think putting them by default is OK?)

Test Plan: Added UIExamples. Checked desktop/mobile.

Reviewers: chad, btrahan, edward

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D5890