Set commandline options to `erlinit`

[Frank Hunleth]

In order to change which OTP init script gets run (among other things), the commandline to erlinit needs to be updated. I don't know the best way of doing this. The current behavior is to pass the Linux kernel commandline on like Linux does when it calls init. The use cases that I can think of would be fine with appending options. I'm not sure that anything would require overriding an option even though that seems like a natural thing to allow.

Before implementing anything, it would be good to propose a syntax and make sure that we all like it. It may be that we need to extend the language.