New assets not displayed in Isolated pool creator

[green-jay]

How to reproduce:

• Add new asset in wallet to UI (e.g. EURC)
• Try creating an isolated pool -> EURC is not in the list

[green-jay]

related #1404

[jvonasek]

Do you have EURC balance?

When asset is not tradable, it will only show up if you have balance.

[DuriSK]

@green-jay as Jakub mentioned above, for XYK pool creator we will display asset as option in asset selector only if you have balance or if its already tradeable any other way (omnipool for example).
My thinking was, how usefull would it be for user to go through x 0 balance assets.
But i can see also other side, that user might be not sure if its even possible to create pool with that asset, if he can not see it there, thats your point?