fixed a lot of issues due to inconsistencies of the code initially
written for Python2, mainly confusions between byte strings
and unicode strings. The new code tries to use byte strings for
file-like streams and unicode strings for in-memory objects.
added JavaDoc strings to document thoroughly functions and methods,
mainly in odf/opendocument.py
added a config.dox file to allow one to build a documentation in HTML
and LaTeX, for library developpers and users.
added many assert() clauses to ensure the types of parameters in
functions and methods
modified the utilities to make them usable with both Python2 and Python3
implemented a feature announced in csv2ods manfiles but not previously
active: -c / --encoding switch to take in account the encoding of
the CSV source file.