[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/general/res/sass/_constants.scss

@@ -124,6 +124,8 @@ $dirImgs: $dirCommonRes + 'images/';
 
 /************************** TIMINGS */
 $controlFadeMs: 100ms;
+$browseToEditAnimMs: 400ms;
+$editBorderPulseMs: 500ms;
 
 /************************** LIMITS */
 $glyphLimit: '\e603';