Extract material for translation following sphinx method

[rufuspollock]

Try out sphinx method for extracting translatable material to see if it works: http://sphinx.pocoo.org/latest/intl.html

If it does work:

• upload sample material to https://www.transifex.net/projects/p/opendatamanual/
• document process
• prepare instructions for translators (probably a separate ticket)

[rufuspollock]

See http://wiki.okfn.org/Open_Data_Manual#Translator