added usage_metrics to full output (#756)

* added extra parameter for kickoff to return token usage count after result

* added output_token_usage to class and in full_output

* logger duplicated

* added more types

* added usage_metrics to full output instead

* added more to the description on full_output

* possible mispacing

src/crewai/utilities/logger.py

@@ -1,6 +1,5 @@
 from datetime import datetime
 from crewai.utilities.printer import Printer
-from datetime import datetime
 
 
 class Logger: