Add some extensibility: configurable cert roots, and not overwriting the hook

[offbyone]

I had some specialized needs:

• I wanted to customize the hook and have it retained, instead of overwritten, so I made that conditional
• I am generating certificates for other network hardware on my synology, so I added support for running this with different certificate configuration

[offbyone]

A trick I just learned: you can suggest changes inline while commenting, using this:

If you do that, then the patches can be done right in the editor :D

[JessThrysoee]

Thanks!