Py3 Fixes

Incorporated contributed fixes for compatibility with Python 3 versions (up to Python 3.8)

Py2/Py3 compatibility + ALICE AIML

• Refactored to make it compatible for both Python2 (tested on 2.7) & Python3
  (tested on 3.4)
• By default utf8-encoded strings are used in Py2 (for backwards compatibility),
  and standard strings (i.e unicode) in Py3
  • This can be changed via the Kernel.setTextEncoding() method.
• Tests moved from inside package to separate test files, and refactored to use
  standard Python unit test infrastructure
• Additional argument chdir to Kernel.bootstrap() method
• aimlvalidate & test scripts install now as package scripts aiml-validate and
  aiml-bot. They have been refactored and contain additional arguments
• The "standard" AIML set has been moved as package data, and installs with it
• Added ALICE AIML v. 1.9 from aiml-en-us-foundation-alice at
  https://code.google.com/archive/p/aiml-en-us-foundation-alice/downloads
  • aiml-en-us-foundation-alice has GNU Lesser GPL license
    (http://www.gnu.org/licenses/lgpl.html)
  • a few AIML 1.9 files have been corrected. Two of them have been commented
    out since they use the AIML 2.0 construct