Apache 2.0/MIT/BSD/CC Licensing

[oursland]

libcose is currently under the LGPL 2.1 license which unfortunately restricts use in systems that utilize static linking, such as microcontrollers. As this library is well suited for the microcontroller use case, I believe adoption would be greatly improved by moving to a less restrictive license.

For my application using the Espressif ESP32 microcontroller, my team and I are prepared to make the necessary additions to the ESP-IDF for inclusion of libcose into the upstream repo as a PR. The only hurdle is that Espressif will only accept code with an Apache 2.0 or compatible license.