Fixes for new aravis API and pixel formats#5

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ojura wants to merge 3 commits intossafarik:masterfrom

createc-uk:master

Commits on Nov 6, 2014

establish compatibility with avaris >= 0.3.6
CaeruleusAqua
committed

Commits on Feb 1, 2016

use image encodings defined in sensor_msgs/image_encodings.h where possible
shaun-createc
committed

Commits on Feb 4, 2016

added frame id to buffer error message
shaun-createc
committed