fix for jenkins-bug #JENKINS-17058

overriding method readResolve() from base-class BPHostConfiguration for
resolving Reflection-problems with XStream
fix for jenkins-bug #JENKINS-17058

overriding method readResolve() from base-class BPHostConfiguration for
resolving Reflection-problems with XStream
fix for jenkins-bug #JENKINS-17058

overriding method readResolve() from base-class BPHostConfiguration for
resolving Reflection-problems with XStream;
removed own SecretHelper (replacement/hiding of the API-class) and
creating new class MySecretHelper;