settlerlib: added interval support for signals with zero channels (empty chains)
chain sensor: added support for additional absolute translation variance
interva_calc: removed non-standard 'typeof' operator
cov_est: added ctrl+c handling
cov_est: show xyz/rpy for non-urdf transforms
Merge branch 'master' of github.com:ros-perception/calibration
Merge pull request #17 from dgossow/master

Added support for empty / low-dimensionality chains