Add Lambda functions for event and place management

[riolaf05]

• Implement delete_event.py for deleting events from DynamoDB.
• Implement get_event.py for retrieving events with filtering options.
• Implement post_event.py for creating new events in DynamoDB.
• Implement update_event.py for updating existing events in DynamoDB.
• Add requirements.txt for boto3 dependency in event API.
• Implement delete_place.py for deleting places from DynamoDB.
• Implement get_place.py for retrieving places with filtering options.
• Implement post_place.py for creating new places in DynamoDB.
• Implement update_place.py for updating existing places in DynamoDB.
• Add requirements.txt for boto3 dependency in place API.
• Create PowerShell script to create users in AWS Cognito User Pool.