#12 Add alternative export option for further automated processing

[mranderson2007]

There is need for an export option from ReadESM into other data formats beside the pretty-printed XHTML that is suited for further automated processing. Pure command line control will presumably suit best for such a purpose, so I guess this is a MUST.

Determining a good output format is subject to discussion. Obvious options include XML and JSON.

My first idea would be to use JSON (which defaults to UTF-8 for character encoding).

(First thoughts about special handling sequences of non-printable characters with special encoding beyond standard JSON esacpe strings turned out to be excessive)