Introduce a poller for the elapsed time of a process

[ryandoyle]

Hi

I've developed a new condition that will automatically restart processes (or perform some other action) if they are alive longer that a certain period of time.

I have re-used the time_string_to_seconds method in PortablePoller as it was only used in tests (and I couldn't get it to work for my use either).

[ryandoyle]

Heya, hoping to get this merged soon as I think others will find this useful as well!

We have been using this patch in production and can verify it is working as expected.

[ryandoyle]

It would be good to know if this is not being considered at all so we can maintain our fork of god.

Thanks