roller should set denoms in the genesis file

[mtsitrin]

as roller defines both the symbol denom (e.g RAX) and the base denom (e.g uRAX),

it should register them both in the genesis under denom_metadata

[mtsitrin]

on genesis, the following should be set in app_state.bank.denom_metadata:

[
	   	{
	   	          "description": "The native token of the rollapp",
	   	          "denom_units": [
	   	            {
	   	              "denom": "u$DENOM",
	   	              "exponent": 0,
	   	            },
	   	            {
	   	              "denom": "$DENOM",
	   	              "exponent": 18,
	   	            }
	   	          ],
	   	          "base": "u$DENOM",
	   	          "display": "$DENOM"
	   	        }
]

[mtsitrin]

handled by #293