Annotation Tool: Flagging plugin should now allow instructors to remove flags from annotations

Annotation Tools: Added lots of comments, fixed spacing, fixed slice issue

Annotation Tools: i18n fixed for this tool

 - fixed Translator to Translators

Annotation Tools: Removed unnecessary class and worked with element object
Merge pull request #4378 from lduarte1991/lduarte-harvardx-pr10

Annotation Tool: Fixed Flagging for Instructor flag removal