One round of proofreading of strings.xml

- add period when appropriate
- remove capitalization (only capitalize first word)
- add a 'title' suffix to title strings
- for Dynamic thresholds, rename to 'Medium Speed Percentage'
  because the value is a percentage.
- tranlstate 'my_tracks_service_name' string.

MyTracks/res/layout/send_to_google_result.xml

@@ -31,7 +31,7 @@ services.
   <TextView
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
-      android:text="@string/send_google_result_title"
+      android:text="@string/send_google_result_header"
       style="?android:attr/textAppearanceLarge"/>
   <TableLayout
       android:layout_width="wrap_content"