Up to [Platon] / libplaton

Doxyfile added into distribution (in future, this file should be
  replaced with Doxyfile.in file).
README slighty update.
TODO heavy update (libplaton future plans described, some problems
  solutions written, etc).

libplaton TODO list
-------------------

- move sources into src/ subdirectory (this directory should better name
  platon/, read further point)
- solve this problem; header and source files of libplaton often need another
  libplaton sources to work, so they do appropriate #include statement;
  although they use #include with relative path such as "../str/strplus.h",
  they should use system #include; so "../str/strplus.h" becomes
  <platon/str/strplus.h>; but note! this should work for headers in libplaton
  distribution and also for headers in system include folder, thus I recommend
  to name sources directory platon/ instead of src/ if we will not found better
  solution
- create doc/ subdirectory for documentation stuff
- document all libplaton sources using Doxygen mechanism
- set appropriate Platon SDG headers to all sources if there is not already
  another header present
- discover mechanism for distribution creation; note, that not all sources in
  libplaton will be included into distribution (such as Atlantis talker
  related); also note, that generated Doxygen documentation _must_ reflect
  state of sources included into distribution
- DocBook documentation
  - not applicable; Doxygen documentation is much better
- think if using Doxygen will not be better for creating documentation
- rebuild building stuff (with focus on filename substitutions in Doxyfile)
- solve standalone headers file position
  - while sources will be its separate directory (such as src/ or platon/, see
    above), they can be in root of this subdirectory