Allow a procedure definition to include custom labels

[paddybyers]

This PR allows a set of custom labels to be declared in any procedure definition, so that each new ticket created for that procedure will include those labels, in addition to the default procedure labels (comply, comply-procedure).

For example, in my procedures/workstation.md I have:

id: "workstation"
name: "Collect Workstation Details"
cron: "0 0 0 15 4 *"
labels:
- "proc-workstation"

(Of course you can go with any alternative yaml list/array syntax.)

I also tried to DRY ticket creation a little bit.

If this is accepted, is it also a good idea to include an empty labels section in each of the template procedures?

[jessesimpson36]

I would also like this functionality. As it stands, I don't really understand the "Audit Tracking" numbers on the Overview tab when GitHub issues are never created with the "audit" flag.