Change XML comment style to avoid mixed whitespace

The previous style required leading tabs followed by five spaces.
Consequently, no autoformatting tools supported it, meaning it had
to be done manually every time, and thus there were many
incorrectly formatted comments around.

Let's change to a comment style that uses only leading tabs, and
is hence autoformattable by standard tools.

Author: ctrueden

pom.xml

@@ -208,8 +208,10 @@ Institute of Molecular Cell Biology and Genetics.</organizationName>
 			<build>
 				<pluginManagement>
 					<plugins>
-						<!-- This plugin's configuration is used to store Eclipse m2e settings
-						     only. It has no influence on the Maven build itself. -->
+						<!--
+						This plugin's configuration is used to store Eclipse m2e settings
+						only. It has no influence on the Maven build itself.
+						-->
 						<plugin>
 							<groupId>org.eclipse.m2e</groupId>
 							<artifactId>lifecycle-mapping</artifactId>