Add non-exiting methods and implement SIGHUP reload

[samurai00]

Hey team! I've tried to make a few small tweaks to our server to hopefully improve its flexibility and add some reload functionality. Here's what's new:

• Added pub fn try_bootstrap(&mut self) -> Result<bool> that doesn't call exit
• Refactored pub fn bootstrap(&mut self) to use the new try_bootstrap method
• Added pub fn run_server(mut self, enable_daemon: bool) -> Result<bool> that doesn't call exit
• Kept pub fn run_forever(mut self) -> ! the same, but now it calls run_server under the hood
• Implemented SIGHUP catching for reloading
• Added an example server_reload to show how to reload within a tokio runtime

Related issues:

• #154
• #292