Bump pom-scijava to version 1.71
Make Data extend Named
Use ImgLib's SpaceUtils::getAxisTypes()
Add getDims() to ImageDisplay

Note that this may appear redundant but will be necessary after refactoring
ImageDisplay's type hierarchy.
Add getDims() method to Dataset
Add note about getPlanePosition() method
Use Imglib2 calibrated intervals

This set of changes involves a reorganization of the basic data classes
(Data, AbstractOverlay, Dataset, ImageDisplay). They are now implementing
different interfaces from the img-metadata project. These changes improve
the ability to support the propagation of calibrated values within IJ2.

Note as part of this commit I removed getExtents() from ImageDisplay.
Delete obsolete classes

The reorganization of data type hierarchy has removed the need for
CalibratedInterval and CombinedInterval. These classes have been replaced
with counterparts in the ImgLib img-metadata subproject.