[Frontend] Added transitional animation to Edit mode

fixes #709
- When going from browse to edit mode, the wrapper
around the object being edited will now transition in
from its edges, and the edit controls toolbar will
animate its height;
- There is no transition applied for going from edit
to browse; to do this we'd need to mod the JS on
exiting to look for the end of an animation event;
- Tested in Chrome, Safari and Firefox;
- May not be smooth with very complex objects
like Layouts with a large number of components;
- Added transitional animations to .l-object-wrapper
and .l-edit-controls;
- New 'animTo' mixin added to _effects.scss;

platform/commonUI/themes/espresso/res/sass/_constants.scss

@@ -14,7 +14,7 @@ $colorAHov: #fff;
 $contrastRatioPercent: 7%;
 $hoverRatioPercent: 10%;
 $basicCr: 3px;
-$controlCr: 3px;
+$controlCr: 2px;
 $smallCr: 2px;
 
 // Buttons and Controls