* Brand new XML Rebuilder (from the Lexer's results) that takes care of creating the words and sentences in their final location instead of doing post-swap and post-merge in XSLT. Get rid of the mergeable attribute and the list of elements equivalent to periods.
* JUnit tests for the XML Rebuilder.
* Deal with elements with unique ID.
* Add a new phase in the main xpl to split the the content around the skippable elements.
* Deal with possible null segments in the LightLexer and in the RuledLexer (not tested with big files).