added the release notes for 2013.08
updated license headers

(No code changes!)
Merge pull request #152 from OlegHahm/release_note

added the release notes for 2013.08
Inform about submodule and added tarballs
fixed formatting
Fix transceiver documentation
Merge pull request #153 from authmillenon/fix_transceiver_doc

Fix transceiver documentation
add debug statement
Merge pull request #158 from mehlis/hwtimer

add debug statement