LPS-42555 fix regression bug - themedeployer/basedeployer generates invalid liferay-look-and-feel.xml

Hi Brian please review code. As you requested I detected stripCDATA and moved it to StringUtil. This issue affects ee-6.2.x and ee-6.1.x (where initial changes were backported) but please note that in 6.1 stripCDATA is present in VelocityTemplateParser, not in Transformer class. Thank you.