Work around potentially buggy DOM implementation Node.getTextContent()

[rolfl]

JDOM 2.x starts using getTextContent() to get the value of Text nodes when converting a DOM document to JDOM in the DocumentBuilder class.

There are potential issues in some DOM libraries, and it is not necessary to do that. To avoid potential bugs, use getNodeValue() instead (like JDOM 1.x did).

Since getNodeValue() comes from DOM1 and getTextContent() comes from DOM3 we should run in to fewer problems with getNodeValue().

See further discussion here: http://jdom.markmail.org/thread/zzg72amluw2gdiht