[INTERNAL][FIX] Content Padding Implementation fix for SplitApp

The selectors of the content padding mixin were not considering the
container-relative classes. This fix changes the implementaton to
correct the behavior for the padding concept in split app mode.

Change-Id: Icd6414a8d18626ae15ab2f60e69df3b062d66c8a
[INTERNAL][FIX] Container content padding qunit fix

Firefox does not allow checks for css("padding"). The tests were fixed
to use the left/right/top/bottom attributes instead

Change-Id: Ibfca3e02df4761597ab4e67faf82b71e383959f9
Merge "[INTERNAL][FIX] Content Padding Implementation fix for SplitApp"
Merge "[INTERNAL][FIX] Container content padding qunit fix"