Refinement pass on editing summary panel.

Updates to canned edit summary choices and wording to sync
with Kenan/Vibha's list.

Used designer's color scheme for canned edit summary buttons.

Centralized WMF colors in single file - changed various places
to reference these colors.

Fixed annoying issues causing search keyboard to be hidden
unexpectedly.

Moved some things out of "Defines" file since they really
didn't need be outside of their respective view controllers
as they weren't referenced anywhere else.

Fix for rotation constraint warning on preview page related
to editing summary panel.

Edit summary panel now animates to its docking position at
bottom of screen smoothly during rotation.

Edit icon now responds more reliably to touch events and
is laid out a bit more neatly.

Fixed annoying "article reloading every time web view
controller was presented" bug.

Refactored article loading code. Also made articles be loaded
at beginning of transition to web view rather than at the end.
Result is even snappier page loads.

Change-Id: Icc17003b1d167c295c3229bb53d2aadea8f6302e