Revert "Standard Maven directory layout"

This reverts commit 5bbd826e2f.
The corresponding changes have been ported into branch "develop".

pom.xml

@@ -439,8 +439,8 @@
           <artifactId>maven-assembly-plugin</artifactId>
           <configuration>
             <descriptors>
-              <descriptor>src/assembly/src.xml</descriptor>
-              <descriptor>src/assembly/bin.xml</descriptor>
+              <descriptor>src/main/assembly/src.xml</descriptor>
+              <descriptor>src/main/assembly/bin.xml</descriptor>
             </descriptors>
             <!-- There are a lot of long file names. Suppress the warnings. -->
             <tarLongFileMode>gnu</tarLongFileMode>