fix: selection API, requestPoolManager and VOI and Scaling

[sedghi]

• change the selection api to not rely on the annotation object (UID is enough)
• add PRE_NEW_STACK_IMAGE event for consumers
• add a check for if the loaded image is prescaled (if it was loaded with the scaling parameters), if so it handles the PT non scaled images
• Fix the CPU rendering for PT images
• Add id to the pool managers
• Fix a bug in the requestPoolManager when a new image is added (interaction priority), it was waiting for a request to be finished before sending the high priority image request
• Fix a bug in requestPool to set the maximum number of requests based on the requestType, previously it was summing all up and comparing them with the current number of requests, it should be per requestType
• Fix prefetching imageIds requests to properly set the prefetch requestType
• Port over the orientation helpers from cornerstone-tools

[JamesAPetts]

Some minor comments.