Rp2

* added generated report localization infrastructure: it's now possible to generate taxes for any country in any language (e.g. Japanese taxes in French). See README.dev.md for details
* added -g command line option to select the language to use for generated reports
* default generators are now specified in the country plugin (so that each country can select their allowed generators)
* allowed accounting methods are now specified in the country plugin (so that each country can select their allowed accounting methods)
* minor fixes in the Legend generation code
* updated documentation with new Localization section and updated Country and Report plugin sections with latest API changes
* added user FAQs

* added HIFO accounting method plugin
* updated documentation and FAQs

* added country plugin for Japan
* small improvements in documentation

* fixed issue 39: if ODS file had numeric unique_id it tripped the type checking system
* added support for generators section in configuration: this allows users to select which generator plugins to run. Also deprecated -l/--plugin CLI options
* updated documentation with new generators section description
* added FAQ

* minor improvements

* new open positions plugin, showing a variety of information on unrealized gains and losses (https://github.com/eprbell/rp2/pull/35)
* minor improvements to documentation