refactor some billing code
update the tests
increase test coverage by going through the simplates
retire the "making the world better" statement prefix

closes #1659
move privacy options to the privacy section
implement editing "number" on "Account" page
allow profile statements in multiple languages

closes #2669
remove ad-hoc `_clip` function, use `excerpt_intro` instead
fix title
drop unnecessary functions
remove obsolete function
move COUNTRIES constant to i18n module
move the initialization of LOCALE_EN back to i18n module
use an OrderedDict for COUNTRIES
use the data from babel for COUNTRIES instead of duplicating it
add a `languages_2` OrderedDict to locales
restrict statement languages
implement upserting and fetching statements
Merge pull request #3016 from gratipay/refactor-billing

Refactor some billing code
implement UI for multilingual statements

also refactors some JS code