Clean up implicit ops classes.
Clean up implicit ops classes.

This commit does a few things:

  1. Annotate all method return types
  2. Fix some counter-intuitive BigInt/Natural behavior
  3. Use slightly faster/clearer cfor loops
  4. Make the CC[A]/Array[A] conversions a bit more robust

non/spire,kevinmeredith/spire,tixxit/spire,codeaudit/spire,AlecZorab/spire,JackSullivan/spire,woparry/spire,guersam/spire,non/spire,siddhartha-gadgil/spire,adampingel/spire,AlecZorab/spire,tixxit/spire,JackSullivan/spire,rklaehn/spire,adampingel/spire,rklaehn/spire,siddhartha-gadgil/spire,codeaudit/spire,kevinmeredith/spire,guersam/spire,woparry/spire