initial working version of teacher dashboard

## Features
- Select and switch between content area
- See competency-level progress for all students
- Expand competencies to see skill-level progress for all students
- Scroll horizontally through students with competency/skill column fixed on left side
- Click a skill block under a student to open the Skill Overview window
- Change competency/skill/student to load different demonstrations list in Skill Overview window
- Expand demonstrations in Skill Overview window to see artifact / comments / reporter / timestamp
- Open Log a Demonstration window from main table or from within a Skill Overview window to pre-fill it
- Add/remove many competencies to a demonstration
- Slider for choosing demonstrated level for each skill
- Toast notification and animated grid update after logging a demonstration

## Limitations / Issues
- Can't add competencies from other content areas when logging a demonstration
- Skill Overview window isn't fully styled
- Can't load different groups of students
- "Load next student" checkbox when logging a demonstration has no effect
- Override icon in Log a Demonstration window and in Skill Overview window has no effect
- There is no "x" icon for clearing skill sliders in the Log a Demonstration window
- Toast notification after logging a demonstration doesn't contain any specific details
- Layout efficiency has not been audited
- Student dashboard is only a static mockup