Update to protobuf 2.6.1

[mfehr]

Provides some new features to protobuf and makes interfacing with Tango code easier.

We first need make sure a couple of things work before we can merge this:

• [x] protobuf_catkin_multiarch [3]

• [x] thirdparty_submodule build [201]

MuMa

• [x] multiagent_mapping_multiarch [1590]
• [x] multiagent_mapping_dataset_bot [260]

MapLab

• [x] maplab_multiarch [39]
• [x] maplab_dataset_bot [11]

[mfehr]

test this please

[mfehr]

retest this please