LS's Viet Nam for VP V.4

- UA change : trade interdiction removed, replaced by a +20% CS bonus against civilizations with more citizens
- UB nerf : divided yields obtained from unit death by 5.

- UA : Removed Naval Melee Units from the UA (I was iffy about that part anyway) ; gave Wet Foot to all Civilian and Great People Units as a compensation
- UI : Removed the possibility to place the UI on Farms and Plantations (no longer is a problem now that the adjacency bonus has been modified + reduces the UI spam)
- UB : Removed the Production bonus from Unit Deaths, but increased the Tourism bonus slightly
- Civ UnitFlags : Darkened the background color a bit to allow for units which have already used up all their actions to be more visible among others

- Fixed problems linked to City Names and Diplomacy dialogues
- Changed the names of the UU1 and UB for better alternatives (thanks @Rosete)
- Reworked the UI after discovering the adjacency function I was using wasn't working for culture
- Buffed the UU1 : removed the Sentry promotion, added Cover I and +1 CS / RCS in exchange. The unit still doesn't strike hard, but it is more difficult to kill.
- Tweak to the UB : removed the base Culture yield, replaced by 1 Faith (meaning the Gold conversion is even more central for the cultural output of the building throughout the game)