Add Hooks to run custom steps pre/post each action

[iversond]

Add a hook system into psadmin-plus so that users can extend psa with custom actions for their domains. For example, after a domain is started, you may want to start a monitoring script and then kill the script before the domain is stopped.

• Add option for PRE/POST/REPLACE for each action
• Support multiple hooks per action
• Support for documenting steps in the .psa.conf or additional file:

---
app:
  start: 
    pre:
      - /path/to/script.sh
      - /path/to/script2.rb

[kbens]

Looks like YAML into Ruby Hashes is pretty easy.

https://www.sitepoint.com/choosing-right-serialization-format/