Remove obsolete ImageJ components

The components migrated as follows:
ij-core                   -> imagej-common, scijava-common
ij-data                   -> imagej-common
ij-ui                     -> imagej-common
ij-ui-awt                 -> imagej-ui-awt, scijava-ui-awt
ij-ui-common-awt          -> imagej-ui-awt, scijava-ui-awt
ij-ui-pivot               -> scijava-ui-pivot
ij-ui-swing               -> imagej-ui-swing, scijava-ui-swing
ij-ui-swing-commands      -> imagej-ui-swing, scijava-ui-swing
ij-ui-swing-script-editor -> imagej-ui-swing
ij-ui-swing-tools         -> imagej-ui-swing
ij-ui-swing-updater       -> imagej-ui-swing
ij-ui-swt                 -> scijava-ui-swt
ij-util-awt               -> scijava-ui-awt
ij-util-swing             -> scijava-ui-swing
Add ImageJ Updater to managed versions

The ij-updater-core component migrated to imagej-updater:
https://github.com/imagej/imagej-updater
Enable ImageJ plugin repository when in dev mode

It is not enough to enable maven.imagej.net as a regular repository;
we have a couple of Maven plugins (scijava-maven-plugin and
imagej-maven-plugin) whose snapshots live there too.

So while in dev mode, let's also turn on the ImageJ Maven repository
for plugins, with snapshots enabled.
Release version 1.166

This introduces imagej-updater at version 0.1.0.

It also stops managing many obsolete ImageJ components, and
enables the ImageJ repository for Maven plugins when in dev mode.