Add config variable for parsing format of members list

[CarrotManMatt]

A config value should be supplied to determine how to parse the members list from the response of the members list URL. The suitable values should be:

• GUILD
• JSON
• XML
• CSV
• YAML
• DSV<char>, where <char> is the delimeter character

This provides more flexibility in the data format of the members list, rather than the currently hard-coded HTML parser for the specific table IDs.

[CarrotManMatt]

The /make-member command will also need to be updated to only accept IDs of the chosen format,