Refactor DataTransfers

[Julusian]

• Summary
  During feat: strict tsconfig and use threadedClass #60 all of the connection logic got reviewed, tested and refactored.
  This has not yet been done for DataTransfers, so this code could be a bit questionable and has a bunch of TODOs for things to check/test/improve

Tasks:

• More unit tests
• Review the logic flow in DataLock and the transfer types. Some bits look a bit broken/unused
• Handle failed commands data transfers better
• Handle waiting for lock in data transfers better