Propagate the specificity to computed values
HSSObject: Don't check for container type in setIsa()
Apply the stack values, not computed ones, in _setIsa()
Check the specificity when setting stack values too

This also removes the unnecessary function nesting with _setStackValue()
Propagate the specificity to the stack values too
Reset the specificity when the computed object to be set is equal to the current
Remove unused function
When forcing values, use the highest value possible, instead of 1
Propagate the specificity to the new value after an expression changed
Layout: Add the top padding of the container to the startY when arranging