Gateway: make an effort to inject plugin metadata

People like to create gateways by calling the constructors directly.
Let's make sure that when they are created in this fashion, methods
of RichPlugin like getInfo() and getPriority() still work correctly.

Author: ctrueden

src/main/java/org/scijava/AbstractGateway.java

@@ -54,6 +54,7 @@
 import org.scijava.platform.AppEventService;
 import org.scijava.platform.PlatformService;
 import org.scijava.plugin.AbstractRichPlugin;
+import org.scijava.plugin.PluginInfo;
 import org.scijava.plugin.PluginService;
 import org.scijava.prefs.PrefService;
 import org.scijava.script.ScriptService;
@@ -86,7 +87,15 @@ public AbstractGateway() {
 
 	public AbstractGateway(final String appName, final Context context) {
 		this.appName = appName;
-		if (context != null) setContext(context);
+		if (context != null) {
+			setContext(context);
+
+			// NB: Make a best effort to inject plugin metadata.
+			final PluginInfo<?> info = PluginInfo.getOrCreate(getClass(),
+				Gateway.class, context.getPluginIndex());
+			info.inject(this);
+			Priority.inject(this, info.getPriority());
+		}
 	}
 
 	// -- Gateway methods --