Systray: Remove old doc

Remove old Main-Class from manifest
Add Class-Path to manifest

apps/systray/doc/README.txt

-Bundled in ../java/lib/ are the  binaries for systray4j version 2.4.1 2004-03-28,
-which is still the latest.
-
-Files are from systray4j-2.4.1-win32.zip.
-
-SHA1Sums:
-	28acaea97816f53d188d01fd88b72e670e67286b  systray4j-2.4.1-win32.zip
-	a7f5e02c3652f3f1a72559e54ee69226b8b97859  systray4j.dll
-	947bd91c483494256cf48ad87c211e8701b4f85b  systray4j.jar
-
-
-systray4j.dll is LGPLv2.1, see ../../../licenses/LICENSE-LGPLv2.1.txt
-systray4j.jar for Windows is LGPLv2.1, see ../../../licenses/LICENSE-LGPLv2.1.txt
-Reference: http://systray.sourceforge.net/
-I2P systray code in ../java/src is public domain.
-
-SysTray is really obsolete. It supports Windows and kde3 only.
-We only instantiate it on Windows.
-
-The java.awt.SystemTray classes added in Java 6
-(and used by apps/desktopgui) are the way to go now.
-
-We could either rewrite this to use SystemTray, or switch to desktopgui.

apps/systray/java/build.xml

@@ -20,9 +20,11 @@
         </depend>
     </target>
 
+    <!-- only used if not set by a higher build.xml -->
     <property name="javac.compilerargs" value="" />
     <property name="javac.version" value="1.8" />
     <property name="javac.release" value="8" />
+    <property name="manifest.classpath.name" value="Class-Path" />
 
     <target name="compile" depends="depend">
         <mkdir dir="./build" />
@@ -62,7 +64,7 @@
         <property name="workspace.changes.tr" value="" />
         <jar destfile="./build/systray.jar" basedir="./build/obj" includes="**/*.class">
             <manifest>
-                <attribute name="Main-Class" value="net.i2p.apps.systray.SysTray" />
+                <attribute name="${manifest.classpath.name}" value="i2p.jar" />
                 <attribute name="Implementation-Version" value="${full.version}" />
                 <attribute name="Built-By" value="${build.built-by}" />
                 <attribute name="Build-Date" value="${build.timestamp}" />