(bug 44228) Template engine: Overriding plain() method

Overriding the messaging system's plain() method in the template engine's Template prototype
assuring IE8 compatibility.

Change-Id: Ia063623abc1068f20bd6e59c8b7396b1f4b9e63c
(bug 44228) Explicit "undefined" check in EditableValue

Using jQuery's $.inArray to check for "undefined" does not work in IE8.

Change-Id: I3ecab59732391e5b2b88964937085a7bee082f4f
Merge "(bug 44228) Template engine: Overriding plain() method"
Merge "(bug 44228) Explicit "undefined" check in EditableValue"