Add javadoc for new trait parameters

Author: MarkEWaite

src/main/java/jenkins/plugins/git/traits/CleanAfterCheckoutTrait.java

@@ -50,6 +50,8 @@ public CleanAfterCheckoutTrait() {
 
     /**
      * Stapler constructor.
+     *
+     * @param extension the option to clean subdirectories which contain git repositories.
      */
     @DataBoundConstructor
     public CleanAfterCheckoutTrait(@CheckForNull CleanCheckout extension) {

src/main/java/jenkins/plugins/git/traits/CleanBeforeCheckoutTrait.java

@@ -50,6 +50,8 @@ public CleanBeforeCheckoutTrait() {
 
     /**
      * Stapler constructor.
+     *
+     * @param extension the option to clean subdirectories which contain git repositories.
      */
     @DataBoundConstructor
     public CleanBeforeCheckoutTrait(@CheckForNull CleanBeforeCheckout extension) {