Implement editing from the Studio container page.

STUD-1306
Make tab name comparison case-insensitive
making chrome scroll up when showing the component menu on the Studio unit page
Refactor test logic for switching editor tabs
maintain scroll position after closing the component editing modal in Studio
small ui fixes in Studio - textbooks upload and loading font-size
removed edit-dialog and uploads css, changed component edit icon to pencil, small css fixes
Fix unit tests
fixed mixin sass
Changes based upon code review comments
Clean up the logic for the edit modal's title
Fix up edit_component so that it doesn't take an unnecessary step argument
removed commented out lines
Add more improvements from the review.
Try to fix the failing JavaScript test
Add unit tests for custom tabs and modal titles
Rebuild the way modals are constructed to support nesting.
Address the next round of review comments.
Fix typo in textbook_spec.js
Improve unit testing of xblock editing