implemented second filter stage in depth packet processor
fixed small bug
added configuration to DepthPacketProcessor, right now just allows to set min and max depth
added options to enable/disable the filters to DephPacketProcessor::Config
Merge pull request #17 from christiankerl/second_depth_filter_stage

- implemented edge aware filter stage in CpuDepthPacketProcessor
- added configuration options to DepthPacketProcessor interface