Pre-processing data, because that's always a good idea

Following the new PPPP v2 spec:

• All data is now compressed via lz4's frame algorithm
• Pre-processors can now be used
  • NoOpPreProcessor is the default used
  • EncryptedPreProcessor can be used to add end to end encryption (of course, this can slow down input/output processing though)

Additionally,

• Error handling is nicer
• Various other minor bugfixes