General Cleanup, update copyright notices, remove some old stuff #74

Job	Run time
docs	2m 17s
lint	38s
test (libcoap-sys, openssl, msrv)	2m 19s
test (libcoap-sys, openssl, stable)	2m 36s
test (libcoap-sys, openssl, nightly)	2m 14s
test (libcoap-sys, gnutls, msrv)	1m 13s
test (libcoap-sys, gnutls, stable)	1m 28s
test (libcoap-sys, gnutls, nightly)	56s
test (libcoap-sys, tinydtls, msrv)	1m 6s
test (libcoap-sys, tinydtls, stable)	1m 22s
test (libcoap-sys, tinydtls, nightly)	1m 6s
test (libcoap-sys, mbedtls, msrv)	1m 11s
test (libcoap-sys, mbedtls, stable)	1m 17s
test (libcoap-sys, mbedtls, nightly)	1m 9s
test (libcoap-rs, openssl, msrv)	2m 30s
test (libcoap-rs, openssl, stable)	2m 12s
test (libcoap-rs, openssl, nightly)	2m 35s
test (libcoap-rs, gnutls, msrv)	1m 16s
test (libcoap-rs, gnutls, stable)	53s
test (libcoap-rs, gnutls, nightly)	1m 8s
test (libcoap-rs, tinydtls, msrv)	1m 22s
test (libcoap-rs, tinydtls, stable)	1m 28s
test (libcoap-rs, tinydtls, nightly)	1m 6s
test (libcoap-rs, mbedtls, msrv)	1m 21s
test (libcoap-rs, mbedtls, stable)	1m 23s
test (libcoap-rs, mbedtls, nightly)	1m 24s
	39m 30s

Provide feedback