Playing with an implementation of Search

- Also added alphabet.ml with is incomplete, but will define the association of
  characters from a file to an internal structure and back. For basic parsing
  and IO.

- The current test.ml file does not compile with an inconsistency in calling the
  local_search function. This is due to an un-exposed tree type in the PTree
  module, and in general the PTopology module. Further type level wizardry will
  be required to get things working.