added error constants to dipydoc.* and improved messages in DipyDoc::diagnosis()
new tags for Dipydoc : 'version' and 'id'
DipyDoc's reading : fixed several tags' names, updated version number (=27)
improved DipyDoc::diagnosis() error messages
error if empty text's file name (=dipydoc corrupted)
modified dipydoc.cpp : updated doc
modified dipydoc.cpp : updated doc
Merge branch 'feature2' into develop