Move acq.currency_code entries and wrap for i18n

Fix LP#1107834 by moving the acq.currency_code entries into
950.data.seed-values.sql and wrapping the texts with oils_i18n_gettext.

Signed-off-by: Pasi Kallinen <pasi.kallinen@pttk.fi>
Signed-off-by: Remington Steed <rjs7@calvin.edu>
Signed-off-by: Ben Shum <bshum@biblio.org>
Move exchange_rate seed data to 950 file

Since currency_type is a foreign key of acq.exchange_rate, if we move
currency_type to the seed data file, exchange rate must follow.

Signed-off-by: Dan Wells <dbw2@calvin.edu>
Signed-off-by: Ben Shum <bshum@biblio.org>