[ADD] Optimise YGG funding logic
Currently , thornode will fund yggdrasil when a pool become active , regardless how much liquidity the pools has. Some of the pools which doesn't have significant amount of liquidity get scattered across more than 50 yggdrasil vaults. This create problems, when a large liquidity provider withdraw , it's outbound get split into many. some edge cases , even asgard doesn't left enough to fulfil the request.
If a pool doesn't have enough liquidity , for example the pool's RUNE depth is less than 500K RUNE , then don't fund yggdrasil