Fix crash in interpretKeyEvents.

cmd.match could return null, but was immediately being indexed. Added a
null check.
Adds debug-mode only property validation to the layout property. Argument and property validation helps developers save time by failing at the root of the problem, providing useful messages and avoiding difficult to diagnose infinite loops. Normally, this type of validation would come at the expense of the performance of an application, but fortunately SproutCore's build tools allow us to separate all of this code entirely from production builds. Win-win!
Fixes an extremely rare security vulnerability in SC.TextFieldView that could occur if a hint overlay is used that included user generated hint. Also fixes @type of applyImmediately.
Removes an invalid condition that prevents key down validation in any browsers that support touch events (which has nothing to do with whether touch events will be used or not).
Fixed layout value warning to accept other valid layout values
Added sanity checks into grid layout computation
Fixed menu UI tests by specifying primary mouse button
Explicitly specifying mouse event pageX and pageY for drag and drop tests
Merge pull request #1234 from jameschao/layout_warning_fix

Fixes for various failing tests
Merge pull request #1230 from sproutcore/team/fairbanksg/interpret-key-events-crash

Fix crash in interpretKeyEvents.
Honor allowsMultipleSelection in SC.CollectionView.

A few keyboard functions were ignoring allowsMultipleSelection when
selecting multiple items.