GROOVY-6621 fix Node#text when value is NodeList

by accounting for non-String children elements
existing difference from o.w.d.Document
Merge branch 'master' into GROOVY-6621-Node-text-when-NodeList-value
in preparation for moving the original tests
move NodeTests to main project
update for changes to text() method
Merge branch 'master' into GROOVY-6621-Node-text-when-NodeList-value
Merge pull request #364 from ml10/GROOVY-6621-Node-text-when-NodeList-value

GROOVY-6621 fix Node#text when value is NodeList