[Click] Default constructor of Timer

[Erwin Van de Velde]

Dear all,

The Timer class has a default constructor, but when you use it (e.g. you 
accidently forget to put fTimer(this) or something like that in your element 
constructor), you are left with a timer that does nothing, even after calling 
the initialize function on the timer. For me this resulted in a bug, which was 
quite hard to find.

So I am suggesting:
- Removing the default constructor of the timer if it has no use (I do not see 
any)
- Adding a click_chatter with a warning in the default constructor if it is 
required.

Best regards,
Erwin