Use proper msg voxel grid manager decoder id 31

* introduce new msg: SlicedPointCloud.msg
* use that new msg file in VoxelGridDownsampleManager and Decoder. (it uses PointCloud2 because of the historical reasons)
* catch error inside of input callback of VoxelGridDownsampleManager to avoid error such as tf exception.

see https://github.com/jsk-ros-pkg/jsk_recognition/issues/31 in ortder to refer discussion before this PR