remove curvemapper from snlite

Created by: zeffii

some snlite pruning.

• removing old directive (curvemapper is now a proper node)
  • also removing all associated functions from helper files, they are now part of the curvemapper files.
• adding alternative parsing for required sockets

  """
  >in socketname type   # for required linked sockets  (no default, no nested specification)
  ...etc
  """

  this > is also a hint to the reader that these sockets are necessary for the code to function. Not all script node scripts will need this, but for the scripts you include in json/examples you might want to add this, it also keeps the testing suite happy.