Update to the imglib2 2.0.0-beta-17 release

This release features the 'nonlinear-goodies' enhancements, which rework
axes to support linear calibration with offset (i.e., "y = m*x + b"), as
well as other nonlinear calibrations generally (i.e., any "y = f(x)"
function you might care to define in a subclass of Axis).
DefaultImageDisplay: fix method order and headers
AbstractData: add missing javadoc
DefaultDataset: avoid NPE if ImgPlus axes are null
DefaultImageDisplay: remove obsolete code
AbstractData: do not serialize AxisTypes

After a lengthy debugging session (thanks to Johannes Schindelin and
Mark Hiner for assistance!), we determined that the current approach
of duplicating Overlays via serialization + deserialization was causing
the AxisType of each CalibratedAxis to be duplicated as well. This
happens via somewhat mysterious means deep inside ObjectInputStream, in
that no DefaultAxisType constructor (not even the usually-very-useful
unlabeled curly braces constructor block!) is ever invoked when the
object is created via deserialization. This phenomenon made it quite
tricky to determine exactly how these objects were coming into being.

The symptom was that the Crop command resulted in rogue X and Y axes
propagating. Since they did not match the canonical X and Y from which
they were replicated, they became additional axes within the
CombinedCalibratedRealInterval, and thus became extra X and Y sliders in
the cropped image display. But surely there were many other lurking bugs
relating to this aspect of Overlay duplication, too.

The fix (for now) is to avoid serializing or deserializing each AxisType
object itself, but rather simply save its label.

Ultimately may also want to rewrite the overlay duplication code to work
in a more conventional manner (i.e., have each subclass define how it
gets duplicated). This is how each CalibratedAxis gets copied right now:
via a copy() method which each leaf subclass overrides. But at the
moment it is actually rather useful to duplicate overlays this way,
since we want overlay serialization to work anyway.
Eliminate use of deprecated DefaultCalibratedAxis

We now use DefaultLinearAxis instead.
WIP: Eliminate uses of deprecated calibration methods