Consider adding Ramp, AbstractTimer and Timer as PqGetters

[sofian]

In fact, Timer should be a PqDigitalGetter and Ramp should be a PqGetter (perhaps even a PqMappable). Currently this is not feasible as since both inhering from AbstractTimer we would get a situation with a "diamond problem" which we want to avoid.

Here is a tentative solution:

• AbstractTimer becomes: class ProgressBar : public PqGetter, public PqMappable (and uses a Chrono inside)
• Timer becomes: class Timer : public PqDigitalGetter (and uses a Chrono inside)
• Ramp becomes: class Ramp : public ProgressBar

Only things are:

• There will be a lot of repetitive code (which is always an issue when trying to avoid multiple inheritance)
• I don't like "ProgressBar" and wish I could find another name (maybe just "Progress"? or maybe we call it "Timer" and rename "Timer" as "Alarm/AlarmClock")

[sofian]

I'm not 100% sure whether we should do this after all cause there are already units that do the job: Metro (similar to Timer but not the same cause it only activates for one frame while Timer is more like a clock that needs to be restarted) and TriOsc (for a repetitive Ramp).

But still ... it could make more sense and be more logical to keep Timer and Ramp to be compatible with the rest of the system. Here is what each do:		Repetitive	Needs restart
Digital	Metro	Timer
Analog	TriOsc	ProgressBar (*)

(*) Ramp also fits in that category as a special / advanced case.