Handle assets with low liquidity (#468)

* Handle assets with low liquidity

`isConsumable` is : 
- 'true' when pool/exchange created and enough datatokens are available ( can we check for exchange?)
- 'false' when pool/exchange created and not enough datatokens are avaialbe
- '' when pool/exchange not created

* isConsumable optional

src/ddo/interfaces/BestPrice.ts

@@ -2,6 +2,7 @@ export interface BestPrice {
   type: 'pool' | 'exchange' | ''
   address: string
   value: number
+  isConsumable?: 'true' | 'false' | ''
   ocean?: number
   datatoken?: number
   pools: string[]