Read accepted fields from config file

[parker67]

get list of accepted fields from a config file instead of hard coded

[ScottyAU]

Done

[parker67]

To clarify, this is for the input from slack. Fields that are accepted by the script should be configurable in the json file.

e.g.

{ "slack":{ "SLACK_BOT_TOKEN" : "", "Fields":["IP","Email","src-ip" etc etc } }