Draft: py4web; create a decorator to recoonect to db

Follow up of MR !1370 (merged).

We make a try to convert reconnect calls as a decorator. It don't work out of the box. Open this MR to remember.

Decorator to check and reconnect tasks to db. It is needed to make a reconnect to DB as each task is launch in his own thread. Without it, we are in a random state where some insertion/deletion/update are poorly propagated without commit call