Replace header version with constant

Author: Caitlin Bales (MSFT)

src/main/java/com/microsoft/graph/core/Constants.java

@@ -12,4 +12,5 @@ private Constants() {
 	public static final String APPID = "app-id";
 	public static final String USERNAME = "[email protected]";
 	public static final String PASSWORD = "password";
+	public static final String VERSION_NAME = "0.1.0";
 }

src/main/java/com/microsoft/graph/http/BaseRequest.java

@@ -31,6 +31,7 @@
 import com.microsoft.graph.options.FunctionOption;
 import com.microsoft.graph.options.QueryOption;
 import com.microsoft.graph.core.ClientException;
+import com.microsoft.graph.core.Constants;
 import com.microsoft.graph.options.HeaderOption;
 import com.microsoft.graph.options.Option;
 
@@ -131,7 +132,7 @@ public BaseRequest(final String requestUrl,
             }
         }
         final HeaderOption requestStatsHeader = new HeaderOption(REQUEST_STATS_HEADER_NAME,
-                String.format(REQUEST_STATS_HEADER_VALUE_FORMAT_STRING, "1.0.0"));
+                String.format(REQUEST_STATS_HEADER_VALUE_FORMAT_STRING, Constants.VERSION_NAME));
         headersOptions.add(requestStatsHeader);
     }