i18n: Make XBlock buttons & components have localizable display names

1. Current code uses type name as the display names for XBlock buttons, so the name of these five buttons can't be localized. This fix contains code that adds a 'display_name' field for the buttons, and makes their names localizable.
2. The display names of components in advanced, html and problem types can be localized now.
Remove some outdated code.
BLD-975: Remove Video player outline.
Add some missing AUTHORS
Allow editing of container xblocks/xmodules

STUD-1312