VoiceCompiler failure

[psibre]

The VoiceCompiler's template files were left out of recent improvements and fixes.
So now, running it fails, for various reasons, with the less-than-informative error,

INFO  VoiceCompiler: Creating directories
INFO  VoiceCompiler: Copying template files
INFO  VoiceCompiler: Copying voice files
INFO  VoiceCompiler: Compiling with Maven
java.lang.Exception: The component VoiceCompiler produced the following exception: 
    at marytts.tools.voiceimport.DatabaseImportMain$8.run(DatabaseImportMain.java:277)
Caused by: java.io.IOException: Cannot run program "mvn" (in directory "[...]"): error=2, No
 such file or directory
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
    at java.lang.Runtime.exec(Runtime.java:620)
    at java.lang.Runtime.exec(Runtime.java:450)
    at marytts.tools.voiceimport.VoiceCompiler$MavenVoiceCompiler.compileWithMaven(VoiceCompiler.java:329)
    at marytts.tools.voiceimport.VoiceCompiler.compute(VoiceCompiler.java:91)
    at marytts.tools.voiceimport.DatabaseImportMain$8.run(DatabaseImportMain.java:274)
Caused by: java.io.IOException: error=2, No such file or directory
    at java.lang.UNIXProcess.forkAndExec(Native Method)
    at java.lang.UNIXProcess.<init>(UNIXProcess.java:248)
    at java.lang.ProcessImpl.start(ProcessImpl.java:134)
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
    ... 5 more

[psibre]

Believing that running mvn will simply work is a pretty strong assumption.
Possibly more robust alternatives might be Maven Invoker or Maven Embedder (see also http://stackoverflow.com/q/5141788), but both require configuration that would be system-specific (such as the path to mvn, so we'd be back we're we started).
We don't want to over-engineer a solution at this point, because the marytts-builder will soon be replaced anyway. So providing a new configurable property with a reasonable default is probably the best solution:

VoiceCompiler.mavenBin /usr/bin/mvn