added com.google.code.gson 2.2.4 dependency for later introduction of the
openconnectome bindings (and because it is great and we will definitely
use it for other remote backends)
test openconnectome
Merge branch 'janelia2' of github.com:tpietzsch/spimviewer into janelia2

Conflicts:
	pom.xml
	src/main/java/bdv/BigDataViewer.java
Catmaid implements mipmapTransforms
transferred and adjusted OpenConnectome backend from imglib2-remote-viewer
Merge branch 'janelia2' of github.com:tpietzsch/spimviewer into janelia2

Conflicts:
	src/main/java/bdv/img/catmaid/CatmaidImageLoader.java