TNL-731: Add possibility to search notes.
Merge pull request #6086 from edx/anton/edxnotes-search

TNL-731: Add possibility to search notes.
TNL-661: Toggle all notes
Addressed comments.
Speed up rendering of notes by setting z-index of certain elements in CSS instead of JS.
Add python unit tests.
Add bok-choy tests.
Add test for decorator.
Addressed second batch of comments.
Removed test.
Save course state.
Addressed third round of comments.
Add tests for Decorator.
Add fixes.
Disable checkbox before initialization.
Add fixes.