A class splitting a Reader into chunks. In a continuous input Reader, search for lines containing a specific "end-of-chunk"
marking (e.g., an XML root end tag), and return individual readers, each of which will provide one chunk (including the line
containing the end-of-chunk marking).
Return a reader from which one chunk can be read, followed by EOF. Chunks are delimited by start of file, lines containing
the end marker string (line is last line in chunk), and end of file. Returns null if nothing more can be read.