init should have respawn rate limits

[egranata]

There should be settings in init configuration to:

• claim that it's OK if a daemon crashes and not to respawn it;
• not respawn a daemon more than N times if it crashes (and either accept that and move on, or panic and hang the system)

[egranata]

There are two axes at work here - and in fact 3:

• can a service "fail" without causing a system-wide panic?
• should a service be fire-and-forget or should init actively wait for a service to exit?
• what does it mean for a service to fail? can't launch? exits? crashes? can it respawn? if so, how many times?

So far, the answers are:

• yes;
• configurable
• error exit if init is waiting for the exit; any exit if it's fire and forget