More process options

[pgjones]

These are possibilities,

• Allow signals to force reload the processes
• Allow signals to to increase and decrease worker count
• Support fork (via preload option?) if possible on the os
• Allow a signal to reload the sockets and hence certs
• Support a max_requests before the process restarts
• Check and ensure workers are always running

[realsama]

+1 Especially for preloading.

[nlnjnj]

+1 Especially for preloading. For ML case