prepare with classifier support

This is a bug fix release to allow your build to use the 'classifier' option for the spring boot jar. This option can be used in your build to create 2 jar files. One regular jar file and one spring boot runnable jar file like this:

jar {
    enabled = true //also build the standard, non-spring boot runnable jar
}

bootRepackage {
    classifier = 'boot' //add 'boot' to executable jar file name
}