sys:transceiver: fix some doxygen comments
Replaced old release notes with the current ones
sys: add utility functions for `struct tm`
Add `struct tm` utility "test"
Merge pull request #1247 from thomaseichinger/transceiver_doc

sys:transceiver: fix some doxygen comments
Merge pull request #1146 from Kijewski/struct-tm-utils

sys: add utility functions for `struct tm`