Use application icons for "Eye" menu and Crumbs

Summary:
Issues here:

  - Need an application-sized "eye", or a "home" icon for "Phabricator Home".
  - Some of the "apps_lb_2x" sliced images are the "_dark_" versions, not the light versions.
  - If you slice an application-sized "logout" (power off) icon and application-sized "help" (questionmark in circle) icon I can replace the current menu icons and nearly get rid of "autosprite".
  - To replace the icons on /applications/, the non-retina size is "4x", so we'd need "8x" for retina. Alternatively I can reduce the icon sizes by 50%.
  - The "Help", "Settings" and "Logout" items currently have a "glowing" hover state, which needs a variant (or we can drop it).
  - The /applications/ icons have a white hover state (or we can drop it).
  - The 1x application (14x14) icons aren't used anywhere right now, should they be? Maybe in the feed in the future, etc?
  - The "apps-2x" and "apps-large" sheets are the same image, but getting them to actually use the same file is a bit tricky, so I just left them separate for now.

Test Plan:
{F26698}
{F26699}

Reviewers: chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T1960

Differential Revision: https://secure.phabricator.com/D4108

Author: epriestley