cubicweb #1382559 [pylint] supress most errors [waiting feedback]

There are an awfull lot of spurious errors/warnings signaled by pylint on cw.

Most of them should be shut down. The current situation impairs proper pylint use on cw/cubes (in conjunction with emacs/flymake for instance).

priorityimportant
typeenhancement
done in<not specified>
load3.000
load left3.000
closed by<not specified>