Restored Variant constructors & equality operators.

git-svn-id: http://urho3d.googlecode.com/svn/trunk@2675 3bd170d8-ddcf-f82c-f583-7a401ccf5608
Fixed editor's Attribute Inspector to reuse the existing component containers before creating a new one. Enhanced Attribute Inspector to change ui-element icon's color based on its 'visible' property.

git-svn-id: http://urho3d.googlecode.com/svn/trunk@2676 3bd170d8-ddcf-f82c-f583-7a401ccf5608