Improve Tradeships.lua

- Preparations:

Add method Ship:GetCargo
Add method Ship:GetDurationForDistance
Add method Ship:Create
Add method ui.treeNode & ui.treePop
Fix ui.Format.Number
Turn off the output when the ship changes frames
Reduce the detection range of hyperspace clouds

- Tradeships.lua

For current system, calculate all possible routes of tradeships,
durations, flows; arrange ships in space in such equilibrium state,
as if the have been flying about their business for a long time.

Calculate the average spawn interval for new ships, and parking
intervals, so that the stations are not overcrowded or empty.

Сreate a tab in the debug window with full information on
routes, ships, stations, remote systems.

data/libs/Ship.lua

@@ -292,6 +292,36 @@ Ship.RemoveEquip = function (self, item, count, slot)
 	return ret
 end
 
+--
+-- Method: GetCargo
+--
+-- Build a table where the keys will be the names of the cargo, and the values
+-- will be their number
+--
+-- > cargo = ship:GetCargo()
+--
+--
+-- Return:
+--
+-- The table where the keys will be the names of the cargo, and the values
+-- will be their number
+--
+-- Availability:
+--
+--  2021
+--
+-- Status:
+--
+--  experimental
+--
+function Ship:GetCargo()
+	local count = {}
+	for _, et in pairs(self:GetEquip("cargo")) do
+		if not count[et] then count[et] = 0 end
+		count[et] = count[et]+1
+	end
+	return count
+end
 
 --
 -- Method: IsHyperjumpAllowed