Index Pool Token <> Token mapping

[gasperbr]

Problem: The UI needs to find the relevant pool addresses for two tokens.
Solution: When deploying an index pool store the pool address under a pools mapping so that every token combination is covered (n*(n-1)/2) combinations.

for(let i = 0; i < pools.length; i++)
for(let j = i + 1; j < pools.length; j++)
pools[tokens[i]][tokens[j]] = pool