Files tab

Acceptance Criteria:
1. be able to drag and drop multiple files to case tab
2. can leave description/comment per file
3. save all files added in a batch into a single activity
4. show progress when files are being uploaded
5. file list section should automatically reflect the new files/activities added
6. Download/Delete action per file
7. Inline edit for file description/comments
8. show tags for the activities (stage 2)
9. Filters including: full-text filter, file type
10. Filter by Activity Category. Default to All Activity Category.
11. Filters by activity tag (stage 2)