Test custom request; Edit .dockerignore

[FabijanC]

Usage

• Return [] instead of {} if invoke fails.

Dev

• Convert test_plugin to shell script.
• Add test/ directory to .dockerignore (should reduce image size).
• Use double quotes consistently throughout project.
• Add endpoint testing (pytest):
  • To enable this, arg parsing had to be done inside the main function.
• Validate calls/transactions in separate methods.