#382 Post-Python 3: Remove obsolete 'history' table and supporting code

[Ahasuerus]

Remove obsolete 'history' table and supporting code. See function authorHistory in https://sourceforge.net/p/isfdb/code-svn/HEAD/tree/branches/p3/mod/aa_update.py and function setHistory in https://sourceforge.net/p/isfdb/code-svn/HEAD/tree/branches/p3/mod/common.py . They were originally created to support Edit History, but the current implementation of Edit History doesn't use them any more.