Signal hound a few more changes

[jenshnielsen]

While trying to resolve a usb comm error for @nataliejpg I cleaned up the driver a bit

• Add types to ctypes dll calls matching the api defined in Signal Hounds headers. The only real changes are a few uint -> int that should have no real consequence as we are dealing with small positive numbers
• Rewrite _get_sweep_data to capture data directly into a numpy array saving a loop over the data
• refactor the averageing logic into _get_sweep_data removing the avg function. This saves a few redundant dll calls
• remove the retry functionality from _get_sweep_data. The api docs are quite clear that there is no point in retrying when the communication is lost. The only way forward is to close the device. All other errors relate to invalid input and will not be fixed by retrying

[codecov]

Codecov Report

Merging #1318 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1318   +/-   ##
=======================================
  Coverage   73.24%   73.24%           
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  Files          85       85           
  Lines        9833     9833           
=======================================
  Hits         7202     7202           
  Misses       2631     2631

[astafan8]

@jenshnielsen merge this if it's ready?

[jenshnielsen]

@nataliejpg confirms that this is working