Double-check translations for Vietnamese

With the help of Crowdin, instead of Text editor which very hard to check side by side (en & vi), i'm double checked every strings for:
- Mis-translation.
- Typo.
- New sentences for some strings.
- Synced some translations. e.g. `wave` => `đợt` (other one is `lượt`)...
- Translated new string from world processor in editor commit (ecfb5ed)

All turret's and unit's names are remain as orginal ones, like previous translations. I don't know if i should translate them, but in other languages, they were translated.