[css-transitions] Describe what the before-style and after-style are when considering whether to start a transition.

This implements part A (and the normative part of part C) of the proposal in
http://lists.w3.org/Archives/Public/www-style/2013Mar/0297.html
as resolved in
http://lists.w3.org/Archives/Public/www-style/2013Jun/0682.html
[css-transitions] Define that transitions do not affect style when animations are running for the same property-element pair.

This implements the group's replacement for part B of the proposal in
http://lists.w3.org/Archives/Public/www-style/2013Mar/0297.html
as resolved in
http://lists.w3.org/Archives/Public/www-style/2013Jun/0682.html
[css-transitions] Add a note explaining that transitions can start on ancestors and descendants at the same time.

This implements the remainder of part C of the proposal in
http://lists.w3.org/Archives/Public/www-style/2013Mar/0297.html
as resolved in
http://lists.w3.org/Archives/Public/www-style/2013Jun/0682.html
[css-transitions] Add a note explaining that values from transitions are inherited normally.

This implements the remainder of part D of the proposal in
http://lists.w3.org/Archives/Public/www-style/2013Mar/0297.html
as resolved in
http://lists.w3.org/Archives/Public/www-style/2013Jun/0682.html
[css-transitions] Add a note explaining that transitions run whether or not they are overridden.

This implements the remainder of part E of the proposal in
http://lists.w3.org/Archives/Public/www-style/2013Mar/0297.html
as resolved in
http://lists.w3.org/Archives/Public/www-style/2013Jun/0682.html
[css-transitions] Remove issue that was resolved by the previous five changesets.