Clean up the code to generate track and waypoint description.

Add DescriptionGeneratorImpl
Make StringUtils constructor private
I18n the strings used to generate the descriptions

MyTracksLib/res/values/strings.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+Copyright 2010 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+<resources>
+  <string name="lib_name">My Tracks Base Library</string>
+</resources>