Port the load(path); function from Fiji's Javascript interpreter

The 'load(path);' function can be used to store libraries of Javascript
code in a central location and reuse them from multiple Javascripts.

It was noted by Christophe Leterrier that this support was not yet
available in SciJava's Javascript support.

The original code was written by yours truly, hence it is easy to
relicense it to BSD as required for this project.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

src/main/java/org/scijava/plugins/scripting/javascript/JavaScriptScriptLanguage.java

@@ -34,6 +34,7 @@
 import java.lang.reflect.InvocationTargetException;
 
 import javax.script.ScriptEngine;
+import javax.script.ScriptException;
 
 import org.scijava.log.LogService;
 import org.scijava.plugin.Parameter;
@@ -58,6 +59,23 @@ public JavaScriptScriptLanguage() {
 		super("javascript");
 	}
 
+	@Override
+	public ScriptEngine getScriptEngine() {
+		final ScriptEngine engine = super.getScriptEngine();
+		try {
+			engine.eval("function load(path) {\n"
+					+ "  importClass(Packages.sun.org.mozilla.javascript.internal.Context);\n"
+					+ "  importClass(Packages.java.io.FileReader);\n"
+					+ "  var cx = Context.getCurrentContext();\n"
+					+ "  cx.evaluateReader(this, new FileReader(path), path, 1, null);\n"
+					+ "}");
+		}
+		catch (ScriptException e) {
+			e.printStackTrace();
+		}
+		return engine;
+	}
+
 	@Override
 	public Object decode(final Object object) {
 		// NB: JavaScript objects come out of the engine wrapped as