Pidfile class improvements

- Renamed `getPid` to `getProcessId` in order to use the same standard
  of other methods;
- Fix wrong file reading:
    I was using `fgets()` so, in the first time you read the file the
    cursor was changed and you could not read the PID again.
Callback action class improvements

- Create method `getHandlers()` to return all defined handlers
- In order to make Callback action reusable all properties was changed
  to `protected`
WIP: Create Daemon action class