PDFBOX-2486: move getActions() method from PDField to PDFieldTreeNode as suggested by Maruan Sahyoun; minor code cleanup

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1640397 13f79535-47bb-0310-9956-ffa450edef68
PDFBOX-2486: use PDFieldTreeNode instead of PDField for preflight field validation to avoid ClassCastException; rename method from french to english; minor code cleanup
PDFBOX-2504: Fix ClassCastException when field children include widget annotations

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1640399 13f79535-47bb-0310-9956-ffa450edef68
PDFBOX-2504: fix formatting

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1640402 13f79535-47bb-0310-9956-ffa450edef68