Update vi.po

Update translate vietnamese
[FIX] #1526 - Missing filename on binary fields download
This is an updated colombian chart of accounts:
- Accounts based on puc.com.co
- adatpations according to current law and last fiscal reform of 2013/14 incorporated (eg. INC, CREE)
- default: 6-numberd, 6th level are account, others views according to colombian PUC regulations
- default accounts predefined according to standard use case
- Most colombian taxes preloaded. Level of detail adjusted to present and future DIAN reporting requirements
- Complete Tax Code layout for generating all necesary transactional fiscal information, Taxes (INC, IVA, CREE), Retentions (ReteIVA, ReteRENTA), Autoretentions (AutoretentionRenta, CREE) - Including predefined cases for import/export, trade with free trade zones, and trade with Companies under the international trade regime
- EXCEPT: ICA Community tax not included, as differs greatly un per city level
[FIX] #1526 - Missing filename on binary fields download
Imprint corrections
Imprint corrections - typo
[FIX] sale_layout: store=True is causing trouble when generating invoices from a pos order
[FIX] models: unexpected missing value when checking for a field in cache

At the end of _prefetch_field(), a check is made to ensure that the cache
contains something for the field to prefetch. The check was incorrect because
the cache was checked for a regular value only.
[FIX] models: improve rationale for the management of flag 'recompute' in context

When the context contains 'recompute': False, the recomputation was not even
prepared. Now both create() and write() prepare the recomputation by invoking
method modified(). The flag only controls whether method recompute() is invoked.
In addintion, the former flag 'no_store_function' was converted to the flag
'recompute', so that both create() and write() use the same flag.

Fixes #1456
[FIX] purchase: purchase buttons on product form only for purchase users
Merge pull request #1790 from thanhchatvn/patch-2

Update vi.po
Merge pull request #1800 from blaggacao/8.0-l10n_co

8.0-l10n_co
[FIX] mail: tell orm to rename column "read" to "is_read"
[FIX] HTML Questions
[FIX] HTML Questions
[FIX] website: correct unslugify of routes