Hooks before and after running an exploiter

[VakarisZ]

We need to refactor HostExploiter abstract class to support hooked functions before and after exploiter execution. One approach would be to rename the method exploit_host to _exploit_host (also on all HostExploiter subclasses), and create a new function exploit_host which will call all the hooked methods and the main method, for e.g. set_start_time, _exploit_host and set_finish_time. In the future, if we'll want to add more logic to before and after exploit, we'll be able to do so easily by overriding _exploit_host.