Update to imglib2-realtransform-2.0.0-beta28

RealViews.constantAffine became obsolete and got removed.
trying to get BDV to compile with upcoming imglib release version
Merge branch 'master' into imglib2-release
Merge remote-tracking branch 'github/imglib2-realtransform-2.0.0-beta28' into imglib2-release
use pom-bigdataviewer as parent
remove unused files
removed everything but core/ and moved everything in core/ to ./
update pom to reflect new repository url