Add tasks for all the new languages

Task/Modular-inverse/Ring/modular-inverse.ring

@@ -0,0 +1,18 @@
+see "42 %! 2017 = " + multInv(42, 2017) + nl
+
+func multInv a,b
+     b0 = b
+     x0 = 0
+     multInv = 1
+     if b = 1 return 0 ok
+     while a > 1
+           q = floor(a / b)
+           t = b
+           b = a % b
+           a = t
+           t = x0
+           x0 = multInv - q * x0
+           multInv = t
+     end
+     if multInv < 0 multInv = multInv + b0 ok
+     return multInv