Feat/add elective units

[sammyrolfe]

Description

Added ability to add search for units and add them as an elective unit on the coursemap.

Type of change

Please delete options that are not relevant.

• [ ] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Tested adding courses with relevant codes and incorrect codes.

tested moving components between elective container and period container.

Testing Checklist:

• [ ] Tested in latest Chrome
• [ ] Tested in latest Safari
• [ ] Tested in latest Firefox

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code in hard-to-understand areas
• [ ] My changes generate no new warnings

[tinahoa]

Hi Sam, It work well on desktop view; however, it lacks responsive styling for mobile views.

[aNebula]

@sammyrolfe - is this PR still relevant or were these changes included in another PR? If it's relevant, then could you please resolve the conflict and open an upstream PR with these changes against new/course-flow branch on doubtfire-lms/doubtfire-web.