Move 'examples/coap-example' to 'examples/coap'

examples/coap/resources/res-plugtest-large-create.c

examples/coap/resources/res-plugtest-large-update.c

examples/coap/resources/res-plugtest-large.c

examples/coap/resources/res-plugtest-links.c

examples/coap/resources/res-plugtest-locquery.c

examples/coap/resources/res-plugtest-longpath.c

examples/coap/resources/res-plugtest-multi.c

examples/coap/resources/res-plugtest-obs.c

examples/coap/resources/res-plugtest-path.c

examples/coap/resources/res-plugtest-query.c

examples/coap/resources/res-plugtest-separate.c

examples/coap/resources/res-plugtest-test.c

examples/coap/resources/res-plugtest-validate.c

examples/coap/resources/res-push.c

examples/coap/resources/res-radio.c

examples/coap/resources/res-separate.c

examples/coap/resources/res-sht11.c

examples/coap/resources/res-sub.c

examples/coap/resources/res-temperature.c

examples/coap/resources/res-toggle.c