Standard datatypes of Fmlib

Some small wrappers around ocamls stdlib modules to facilitate more functional programming. E.g. the module 'Option' and 'Result' support the 'let*' operator. The module 'Array' has a 'push' operation to append functionally elements at the end.

Besides some wrapper around Stdlib modules it has the additional modules:

• Deque: A double ended queue with efficient pushing of elements from the front and the rear end and efficient popping of elements from the front end.

• Btree: Finite sets and maps based on B trees. B trees have better cache efficiency and locality than AVL or Redblack trees.