docs($http): describe how to remove a header on a per request basis

Closes #10144
style($http): make jscs happy
docs($filter): clarify what is a valid filter name

Also updates the CHANGELOG to add info about this breaking some
previous invalid uses of $filter

Closes #10054
Closes #10131
docs(ngShow/ngHide): add spaces to improve readability of CSS

Closes #10101
docs(ngBindHtml): fix awkward wording

Fixes #10097
Closes #10129
style(ngBind): remove trailing whitespace
docs(ngAnimate.$animate): fix classes during the various animation phases

Closes #10124