REACH-31: Implement session manager

Pool of `DynamoViewModel` is created to minimize delay for a newly connected user. Server works in headless mode as a side effect of these changes.
This method requires a bit more documentation, although we know it is meant to clean-up the workspace, but we don't know it is clearing the library items from the search model. Also, the parameter ```DynamoViewModel item``` can be improved by making it ```DynamoViewModel viewModel``` :)