Start to allow multiple sift for one object

Conflicts:
	blort_ros/src/gltracker.cpp
	blort_ros/src/nodes/tracker_node.cpp
Factorize code for ObjectEntry vector reading

Conflicts:
	blort_ros/CMakeLists.txt
Fully implement multiple sift files per object

Conflicts:
	blort_ros/src/gldetector.cpp
Return the pose with the best confidence
Move ObjectEntry.h to correct include directory
Add an example config file for multi sift tracking

The example config highlights all possible patterns
Merge pull request #16 from gergondet/topic/MultipleSiftPerObject

Topic/multiple sift per object