Image compression
(cherry picked from commit 89a70d8a678d09a2807f7b2a592da6559f4fb519)
some neccessary changes
(cherry picked from commit 5fd6e18fe1c52ca1635c723a19f35d66b380ae6d)

Conflicts:
	core/serialization.cc
fix submodule HEAD
(cherry picked from commit 3d054e3d4e3df6020f0c168e005cd4ff5e7fe277)
Protobuf image data type changed from int32 to bytes
(cherry picked from commit 48f28bdae2459ba2bd44a127b8ecc5cf5add4abe)
f
(cherry picked from commit 26f751be35cf7a0dd6dd3f676013a8e2289a2922)
Merge pull request #127 from it-workshop/wp-1.0.0/CAROLINE-3/2

Wp 1.0.0/caroline 3/2