Merge pull request #4 from voer-platform/bug-fixes

Bug fixes: 
- Checkin material
- Correct text body of migrated material
Add migrate on shell script
Merge pull request #5 from voer-platform/bug-fixes

Fix silly issue of generating material ID
Update nginx config file & migration script
Readd isMissing() inside migration script
Start implementing cache to models
Update the log mechanism, add more fields
Change API log to using decorators
Resolve conflict before merging with logging
Update the collection export
Fix incorrect collection JSON when exporting
Add function for checking missing modules
Add new function to migrating script
Fix issue of saving closed material file
Complete the collection migrating script
Add version into migrating script
Move a function from migrate.py to migrate_col.py
Add function to correct some persons UIDs
Correct case with ugly person ID
Fix some bugs inside migration and filtering materials