Restore imagej.version property

We need a version property matching the artifactId of the artifact,
which in this case is net.imagej:imagej, for the melting pot to work.

I considered renaming net.imagej:imagej to net.imagej:imagej2, but
that would disrupt a large ecosystem of downstream code, including
e.g. PyImageJ, which defaults to using net.imagej:imagej currently.
It would be possible to do this rename later, but it would be more
involved, and I would prefer to do it at a time when the rest of the
system is not in motion so much.

Author: ctrueden

pom.xml

@@ -417,6 +417,7 @@
 
 		<!-- ImageJ2 - https://github.com/imagej/imagej2 -->
 		<imagej2.version>2.2.0</imagej2.version>
+		<imagej.version>${imagej2.version}</imagej.version>
 
 		<!-- ImageJ 1.x - https://github.com/imagej/ImageJA -->
 		<imagej1.version>1.53d</imagej1.version>
@@ -1491,7 +1492,7 @@
 			<dependency>
 				<groupId>net.imagej</groupId>
 				<artifactId>imagej</artifactId>
-				<version>${imagej2.version}</version>
+				<version>${imagej.version}</version>
 			</dependency>
 
 			<!-- ImageJ 1.x - https://github.com/imagej/ImageJA -->
@@ -4367,7 +4368,7 @@
 				</file>
 			</activation>
 			<properties>
-				<imagej2.version>LATEST</imagej2.version>
+				<imagej.version>LATEST</imagej.version>
 				<ij1-patcher.version>LATEST</ij1-patcher.version>
 				<imagej-common.version>LATEST</imagej-common.version>
 				<imagej-deprecated.version>LATEST</imagej-deprecated.version>