Update README.md

Update to reflect the changes to Ingress and Storage feed event fields in Carbon Black server 4.2.1
Update README.md

Update watchlist event fields based on Carbon Black 4.2.1 feature set
Update README.md

Fix small typos in field names, add os_type field to binary events
Update README.md

Add os_type field information into process and binary API endpoints
Update README.md

Fix minor typo in field documentation
Merge remote-tracking branch 'origin/4.2.1'