Allow users to permanently hide "share" buttons in settings

Many users do not have other social network profiles and do not want to see the share buttons on all of their content. Add a check box in settings that allows users to permanently hide share buttons everywhere on the site.

• [] Add a checkbox for "hide share buttons" in the settings panel
• [] Hide share controls for users with this flag enabled
• [] make sure the share bar doesn't block ones view when composing a comment when the 'reply' bubble occupies the same region as the bar. If you move the page so the bar is 'out of the way' it auto-reoccupies its blocking position immediately when typing is resumed.
• [] e2e tests
• [] unit tests