Fix Use Cases Diagram
Rename Activity Diagrams

From 'Main' to corresponding names
Add sub-activity 'Create Directory' for 'CRUD'
Add sub-activity 'Rename' for 'CRUD'
Add sub-activity 'Delete' for 'CRUD'
Add sub-activity 'Upload' for 'CRUD'
Fix 'CRUD' Activity Diagram

Replace large block to sub-activities