Fixed state of spam button.
New approve/unapprove icons.
Moderation buttons are now evenly spaced.

Used auto layout to center the buttons in a container view in `bottomView`.

Also added padding to bottom of scroll view so the buttons don't bump up near the tabs at the bottom.
Fixes `by` label text from displaying under the time button.
Adjusted `indicatorView` so that completely covers button content.
Fixes trailing whitespace in `WPContentView.m`
Merge pull request #2230 from wordpress-mobile/issue/2213-comment-moderation-punchlist

Issue/2213 comment moderation punchlist