Add MinimumGasPrices and BlockGas to Mempool from configs

[vladjdk]

Get app.toml and client.toml data into app.go so that they can be used in the mempool.

Refs:

#387 (comment)
#387 (comment)

[linear]

EVM-210 Add MinimumGasPrices and BlockGas to Mempool from configs