Issue #378: remove outdated checkstyle integration files

Author: rnveach

config/suppressions.xml

@@ -16,7 +16,8 @@
     <suppress checks="ImportControl" files=".*[\\/]src[\\/]test[\\/]"/>
     <!-- END of legacy code -->
 
-
+    <!-- empty file is needed for backwards compatibility -->
+    <suppress checks="RegexpMultiline" files="checkstyle\.properties"/>
     <!-- parsing of xml imply reference attribute names, does not make sense to move all to special variables -->
     <suppress checks="MultipleStringLiterals" files="CheckstyleProfileImporter\.java"/>
     <!-- till https://github.com/checkstyle/sonar-checkstyle/issues/135 -->