Refactoring

[aarani]

We should do a refactoring as soon as our backlog is finished (because I don't want to spend hours solving conflicts everywhere), I want to keep track of what should be done here.
- Change the naming scheme for Async functions: #56 (comment) #71
- Get rid of FSharpUtil in favor of fsdk #59 (comment)
and #59 (comment) #55

• The naming scheme in the Utility namespace is all over the place (Utils, Util, Utility)
  - Functions that should be internal:
  TorStream's Accept: https://github.com/nblockchain/NOnion/blob/965cb6d/NOnion/Network/TorStream.fs#L435
  TorStream's ConnectToService: https://github.com/nblockchain/NOnion/blob/965cb6d/NOnion/Network/TorStream.fs#L464
  There are more of these in TorCircuit, we don't even have Task-based functions for them because we don't expect anyone to actually call them. If that's the case we might as well make them internal. Network: hide HS methods from public API #68
• Primitive Obsession when dealing with Keys (we handle everything as byte array)
• Now that we have mailbox, we can maybe add non-Async(sync) functions where ever we can
  - Support for multiple streams over the same HS clientServices,Tests: create HS streams on demand #67