don't use cursors in threaded code, they're not thread-safe
fix traceback hack in `threaded_map()`
fix test
inline `mark_charge_failed()`
Merge pull request #3007 from gratipay/fix-payday-threading

Fix payday threading
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