Fix invalid HTML in templates.

HTMLBars (coming soon in Ember 1.10) validatest templates during
compilation. This PR fixes errors identified.
Merge pull request #4727 from rwjblue/fix-template-html

Fix invalid HTML in templates.
Remove PostSettingsMenuView.

It seems that the properties this sets up (`datePlaceholder` and
`publishedAt`) are unused throughout the project.
Merge pull request #4728 from rwjblue/remove-unused-view

Remove PostSettingsMenuView.
Merge branch 'master' of https://github.com/TryGhost/Ghost

Conflicts:
	core/client/templates/modals/delete-tag.hbs