Revised compilation of the SCSS for the war file (vaadin/grails)

Create or add scripts/_Events.groovy and include this. This now just takes all the Themes there (indicated by a styles.scss file there), compiles the styles.css and removes all the **/*.scss files from the target.

import com.vaadin.sass.internal.ScssStylesheet

eventCreateWarStart = { name, stagingDir ->
    new File("${stagingDir}/VAADIN/themes/").eachDir {
        def scssName = "${it}/styles.scss"
        if (new File(scssName).exists()) {
            ScssStylesheet scss = ScssStylesheet.get(scssName)
            def outFile = new File("$it/styles.css")
            ant.delete(dir:"${it}", includes: "**/*.scss", verbose: true)