Enh/Fix/Clean: Added a select function which return a generator that will yields rows per rows.

+ Use fetchmany() with arraysize of 1024.
+ many pythonization.
+ no return in __init__.
+ select yields list or results/rows per list of results.
  So need to getitem() one more time.
+ Clearly log max_logs_age when given one isn't valid (or isn't given).
Fix tests: need to mock livestatus.handle_request().

+ ah, we need shinken..
+ need importlib.
+ Fix: still need mongodb module for now.
     until shinken tests remove its required dependency.
+ need livestatus test files.
+ Also clean tmp in setUp.
  So that the temp files of an interrupted test doesn't collide with us.