Enforce stricter naming conventions for package names

Change-Id: I84a73a3a997ed25059fc3319db9f013db6e94a4c
diff --git a/tools/build/conf/src/main/resources/onos/checkstyle.xml b/tools/build/conf/src/main/resources/onos/checkstyle.xml
index e04479c..fc6757a 100644
--- a/tools/build/conf/src/main/resources/onos/checkstyle.xml
+++ b/tools/build/conf/src/main/resources/onos/checkstyle.xml
@@ -160,7 +160,9 @@
 
         <module name="MemberName"/>
         <module name="MethodName"/>
-        <module name="PackageName"/>
+        <module name="PackageName">
+            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
+        </module>
         <module name="ParameterName"/>
         <module name="StaticVariableName"/>
         <module name="TypeName"/>