First simple implementation of a DAWG.

The minimal functionality have been implemented, accompanied by tests.
More to come.
Add tests with Chinese characters [TESTS BREAK]

These tests explicit a defect in the implementation, that for now do not properly handle unicode.
Fix handling of unicode characters.
Remove nodeValue type.

It was an indirection that just made things more complicated, for apparently no gain.
Cummulatively increase prefix, instead of slicing the word.
Change order of statements.

It seems saner to do current = next in the end.