[Bug-apl] Erlang Interface into GNU APL

[Juergen Sauermann]

Hi,

I have finished the first version of an Erlang interface into GNU APL, SVN 901.

The idea is roughly this:

1. The Erlang Interface gives you the possibility to carry out computations on larger
    data sets in APL rather than in Erlang. Erlang is a cool language (see www.erlang.org),
    but is a little weak when it comes to heavy computations on large amounts of data.
   This gap can now be filled by means of GNU APL.

2. Based on the Erlang interface you can then also use other Erlang based languages
    to access GNU APL. In particular Elixir (see www.elixir-lang.org).

3. Based on this Elixir interface you can finally use powerful web frameworks based on
    Elixir. In particular the Phoenix framework (see www.phoenixframework.org).

The Erlang interface of GNU APL is essentially Dirk Laurie's libapl (so GNU APL is built
as a library) plus some native Erlang functions that convert Erlang data structures into
APL arrays and start an APL workspace under the hood). The functionality of the interface
is essentially:

- execution of APL commands, including )LOAD, )DUMP, etc. for the manipulation of workspaces,
- creation of APL functions and variables (this is to avoid unnecessary conversions between Erlang
  data structures and APL arrays)
- direct access (call) to every APL function or operator (built-in or user defined)
- evaluation of entire APL statements

Hope you like it,
Jürgen