Create a separate function for asset satoshis and their representation with fractional part

Currently, we have only one function implemented for assets generation in NAI format, e.g.: chainApi.hive(3). This can mislead users into thinking they are paying someone 3.000 HIVE which is just 0.003 HIVE.

We could create a separate function for such usage, e.g.: chainApi.hive_satoshi(3000), which would be equivalent to: chainApi.hive(3) (multiplied by 1000).

This could also mean that we accept numbers with fractional parts: chainApi.hive(3.002) -> 3.002 HIVE