init: allow customizable restart and timeout periods for services

Allow services to specify a custom restart period via the
restart_period service option.  This will allow services to be run
periodically, such as a service that needs to run every hour.

Allow services to specify a timeout period via the timeout_period
service option.  This will allow services to be killed after the
timeout expires if they are still running.  This can be combined with
restart_period for creating period services.

Test: test app restarts every minute
Change-Id: Iad017820f9a602f9826104fb8cafc91bfb4b28d6