add AndroidManifest parser for reading directly from APKs

This will make our algorithm choices a lot more flexible both in terms of
the Installer process and the swap repo process.

app/src/test/java/org/fdroid/fdroid/AndroidXMLDecompressTest.java

@@ -0,0 +1,51 @@
+package org.fdroid.fdroid;
+
+import org.junit.Test;
+
+import java.io.File;
+import java.io.FilenameFilter;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+
+public class AndroidXMLDecompressTest {
+
+    String[] testDirNames = {
+            System.getProperty("user.dir") + "/src/test/assets",
+            System.getProperty("user.dir") + "/build/outputs/apk",
+            System.getenv("HOME") + "/fdroid/repo",
+    };
+
+    FilenameFilter apkFilter = new FilenameFilter() {
+        @Override
+        public boolean accept(File dir, String filename) {
+            return filename.endsWith(".apk");
+        }
+    };
+
+    @Test
+    public void testParseVersionCode() throws IOException {
+        for (File f : getFilesToTest()) {
+            System.out.println("\n" + f);
+            Map<String, Object> map = AndroidXMLDecompress.getManifestHeaderAttributes(f.getAbsolutePath());
+            for (String key : map.keySet()) {
+                System.out.println(key + "=\"" + map.get(key) + "\"");
+            }
+        }
+    }
+
+    private List<File> getFilesToTest() {
+        ArrayList<File> apkFiles = new ArrayList<File>(5);
+        for (String dirName : testDirNames) {
+            System.out.println("looking in " + dirName);
+            File dir = new File(dirName);
+            File[] files = dir.listFiles(apkFilter);
+            if (files != null) {
+                apkFiles.addAll(Arrays.asList(files));
+            }
+        }
+        return apkFiles;
+    }
+}