Added some missing math functions from lua

Barotrauma/BarotraumaShared/Lua/DefaultLib/Utils/Math.lua

@@ -0,0 +1,21 @@
+math.lerp = function (a, b, t)
+    return a * (1 - t) + b * t
+end
+
+math.clamp = function (value, min, max)
+    return math.max(min, math.min(max, value))
+end
+
+math.round = function (value, decimals)
+    decimals = decimals or 0
+    local mult = 10 ^ decimals
+    return math.floor(value * mult + 0.5) / mult
+end
+
+math.sign = function (value)
+    return value >= 0 and 1 or -1
+end
+
+math.remap = function (value, inMin, inMax, outMin, outMax)
+    return outMin + (outMax - outMin) * ((value - inMin) / (inMax - inMin))
+end