Avoid name-conflicts with python.el as much as possible

Docu updated
`which-func-mode' misses class, lp:1160022, fixed

`py-which-def-or-class', new command
now used `which-function-mode', doesn't rely on index
`fill-paragraph' corrupts the paragraph, lp:1162912, fixed

docu updated
TAB results in never ending process, lp:1163423, fixed