Add in memory log

logcat doesn't really support showing logs see
https://stackoverflow.com/q/12692103/4244993
Solution is to delegate to the logcat log and save the logs in memory
that it can be viewed later.

android/app/src/main/java/de/gotify/Log.java

@@ -0,0 +1,44 @@
+package de.gotify;
+
+import java.text.SimpleDateFormat;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Date;
+import java.util.List;
+import java.util.Locale;
+
+public class Log {
+    private static final SimpleDateFormat FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS", Locale.ENGLISH);
+    private static final List<String> LOG = Collections.synchronizedList(new ArrayList<String>());
+    private static final String TAG = "gotify";
+
+    public static void i(String message) {
+        i(message, null);
+    }
+
+    public static List<String> get() {
+        return LOG;
+    }
+
+    public static void i(String message, Throwable throwable) {
+        log("INFO", message, throwable);
+        android.util.Log.i(TAG, message, throwable);
+    }
+
+    public static void e(String message) {
+        e(message, null);
+    }
+
+    public static void e(String message, Throwable throwable) {
+        log("ERROR", message, throwable);
+        android.util.Log.e("gotify", message, throwable);
+    }
+
+    private static void log(String type, String message, Throwable exception) {
+        if (exception == null) {
+            LOG.add(String.format("%s: %s - %s", type, FORMAT.format(new Date()), message));
+        } else {
+            LOG.add(String.format("%s: %s - %s%s%s", type, FORMAT.format(new Date()), message, "\n", android.util.Log.getStackTraceString(exception)));
+        }
+    }
+}