Circumvent problem with implicits

the time limit for the replay is the max of the time limit
given initially and twice the time taken by the prover
(if the result was "valid")

E.g, if Alt-Ergo said valid in 4.9 seconds, for an initial limit of 5,
then the replay will give 10 seconds

also, remove all customization from the Z3 3.x section in prover detection.
I find it morally wrong to chase magic options of a closed-source program.
We should add an option for a prover only when we have clear understanding
of what it does and good reasons to believe that it is useful in our case.

- add the provers list which can be found in the session.
- remove Detected/Undetected since we use only the information
provided by the session, not which provers are currently available
on the current computer.