Implement automated testing

[farlepet]

Create set of test cases to test functionality, likely utilizing coap-client to generate various sorts of requests.

[farlepet]

Preliminary set of test cases:

• [x] Formatting
  • [x] Plaintext
  • [x] Base64
  • [x] Hex
  • [x] Transports
  • [x] UDP
  • [x] TCP
  • [x] DTLS
  • [x] TLS
  • [x] Command execution
  • [x] Stdin value
  • [x] Variable replacement
    • [x] COAPSERVER_PAYLOAD
    • [x] COAPSERVER_RESOURCE
    • [x] COAPSERVER_METHOD
  • [x] Max execution time
  • [ ] Request methods
  • [ ] PUT
  • [ ] POST
  • [ ] GET
    • [ ] Resource observation
  • [ ] Resources
  • [ ] Static resources
  • [ ] Resource templates
  • [ ] Dynamic resources
  • [ ] Log file creation
  • [ ] Multi-block requests