Sample Reading Changes

[nocarryr]

Note that I committed these changes on top of PR #1 so those changes are also showing up here (sorry)

• sdr parameters, open/close methods, etc live in SampleReader
• signal processing parameters and tracking variables live in SampleProcessor
• samples are stored in SampleBuffer then read by SampleProcessor
  • The sample read length is no longer dependent on the number of samples needed for processing
• samples are read in a separate thread then processed in the main thread