Deep/Shallow water - restrict ships/better visibility

[jt-traub]

Most of this is taken from discussion on the NewOrigins discord (#neworigins-v7-talks channel)

@Balvatah

as for ocean ships, then here is the list:
1) Add ability to see into ocean from the coast. The visibility must be 2 regions. It can be connected to some kind of watchtower or other structure. Without structure you can see just 1 region or don't see anything.
2) Ships will need all MP to port on the shore. If you watch your coast then there will be 1 turn to react.
3) Introduce shallow ocean and deep ocean. Small ships and swimming units can travel only shallow waters.
   Deep ocean / big ships can travel deep waters :). Deep ocean ships needs harbor / port to stay on land.
4) Add harbor/ port structure that can be built in the cities. It will allow big ships to port there. Port allows to enter it without waiting one turn.
5) War ships can port everywhere and don't need harbor.
6) Ships see 2 regions around them in the ocean
7) Have one small ship that allows to port at any time (of course for the pirating 🙂 )

Three ship classes: Small Ships, (Big) Merchant Ships, Warships
New structure: Port
Updated structure: Tower (allows to see the shore)
Mechanic change: Deep and Shallow water, swimmers can enter only shallow water 

Small ships probably can always port directly, they can't go over the deep water anyway.
Small ships: Raft, Longship
Merchant ships: Cog, Galleon
Warships: Corsair, Galley, (?) War Galleon

@melf & @balvatah & @chthonic underground

Melf: For Miskatonic, we check for a nearby land hex and prevent LIZA from moving out into open water
Balvatah: Several ocean terrain types is not a problem, just a map generator topic. Many games had such a feature.
Chthonic: I would keep the coastal vs ocean-going distinction for warships and have them just provide additional defence like buildings. Might add a small speed-2 coastal warship to the mix - 10 IRWD, capacity 100, needs SHIP 4, +2 to defences.