Add libusb-1.0-0-dev for Travis OpenNI support
Improve doxygen doc return
Merge pull request #705 from VictorLamoine/doxygen_improvments

Improve doxygen doc return
Revert "Merge pull request #705 from VictorLamoine/doxygen_improvments"

This reverts commit 5743ecb231d689a883674454d3bf1c1bf8c2bc58, reversing
changes made to 649ed559ac99675902e4bba619bff96395a315dd.
Merge pull request #698 from jspricke/travis_openni2

Add OpenNI2 support to Travis