Add more checkstyle tests

- Lines containing tab(s) after space
- Usage of printStackTrace
- Usage of println
- Add SupressionCommentFilter module

SuppressionCommentFilter can be enabled with
// CHECKSTYLE:OFF
and disabled with
// CHECKSTYLE:ON

config/checkstyle.xml

@@ -6,6 +6,7 @@
 	<module name="SuppressionFilter">
 		<property name="file" value="config/suppressions.xml"/>
 	</module>
+	<module name="SuppressionCommentFilter"/>
 	<module name="Header">
 		<property name="headerFile" value="config/header.txt"/>
 		<property name="ignoreLines" value="3"/>
@@ -22,6 +23,10 @@
 		<property name="format" value="^\s+$"/>
 		<property name="message" value="Line containing only whitespace character(s)"/>
 	</module>
+	<module name="RegexpSingleline">
+		<property name="format" value="^ +\t+"/>
+		<property name="message" value="Line containing tab(s) after space"/>
+	</module>
 	<!-- TODO enable this once eclilpse does no longer add javadoc with trailing whitespaces
 	<module name="RegexpSingleline">
 		<property name="format" value="^.*\S+\s+$"/>
@@ -29,6 +34,7 @@
 	</module>
 	-->
 	<module name="TreeWalker">
+		<module name="FileContentsHolder"/>
 		<module name="UnusedImports">
 			<property name="processJavadoc" value="true"/>
 		</module>
@@ -40,5 +46,15 @@
 		<module name="GenericWhitespace"/>
 		<module name="EmptyStatement"/>
 		<module name="PackageDeclaration"/>
+		<module name="RegexpSinglelineJava">
+			<property name="format" value="printStackTrace"/>
+			<property name="message" value="Usage of printStackTrace"/>
+			<property name="ignoreComments" value="true"/>
+		</module>
+		<module name="RegexpSinglelineJava">
+			<property name="format" value="println"/>
+			<property name="message" value="Usage of println"/>
+			<property name="ignoreComments" value="true"/>
+		</module>
 	</module>
 </module>