new interface method ObjectCache.getStatistics

the statistics of a cache instance for an application can be retrieved
by calling `app.__app__.getCacheStatistics()`. That's not very useful for the 
default `ObjectCache` but essential for looking into what more complex cache
impls like `SwarmCache` do

we could remove all the other cache statistics methods like `getCacheUsage` 
and output that info in the map returned by `getCacheStatistics()`

i had to bump java to 1.5 for the generics.. if that's a problem we can
remove the generics

build.xml

@@ -102,8 +102,8 @@
         <replace file="${build.work}/src/helma/main/Server.java"
             token="__builddate__" value="${TODAY}"/>
         <javac srcdir="${build.work}/src"
-            source="1.4"
-            target="1.4"
+            source="1.5"
+            target="1.5"
             destdir="${build.classes}"
             debug="${debug}"
             deprecation="${deprecation}"

src/helma/framework/core/Application.java

@@ -834,6 +834,13 @@ public final class Application implements Runnable {
         return nmgr.countCacheEntries();
     }
 
+    /**
+     * Returns a map of cache statistics
+     */
+    public Map getCacheStatistics() {
+        return nmgr.getCacheStatistics();
+    }
+
     /**
      *  Set the application's root element to an arbitrary object. After this is called
      *  with a non-null object, the helma node manager will be bypassed. This function

src/helma/objectmodel/ObjectCache.java

@@ -110,4 +110,8 @@ public interface ObjectCache {
      */
     Object[] getCachedObjects();
 
+    /**
+     * Returns a map of statistics about the cache
+     */
+    java.util.Map<String,Object> getStatistics();
 }

src/helma/objectmodel/db/NodeManager.java

@@ -1718,6 +1718,13 @@ public final class NodeManager {
         }
     }
 
+    /**
+     * Returns a map with statistics about the cache
+     */
+    public Map getCacheStatistics() {
+        return cache.getStatistics();
+    }
+
     /**
      * Add a listener that is notified each time a transaction commits
      * that adds, modifies or deletes any Nodes.

src/helma/util/CacheMap.java

@@ -331,6 +331,12 @@ public class CacheMap implements ObjectCache {
         return new HashMap(capacity, loadFactor);
     }
 
+    public Map<String,Object> getStatistics() {
+        Map<String,Object> stats = new HashMap<String,Object>();
+        stats.put("size", size());
+        stats.put("threshold", threshold);
+        return stats;
+    }
 }