Job handler update.

[IPMegladon]

• Created combined job handler between python + agent.
• Fixed agent scripts not returning function handles to jobs, which was causing job kill not to work.
• Added startup -S script as a job so it can be unloaded.
• Fixed import script.js with job handling so script can be unloaded later.
• Fixed crashes caused by new InvocationListener(), as InvocationListener cannot be initialised.
  -> Suspect this is the culprit behind a few of the gh issues.
• Migrated job interface to a class and internalised some logic to avoid duplicated code.
• Fixed jobs kill autocomplete.