Add params --tomox.mongodb.name --tomox.mongodb.url

[thanhson1085]

Currently, we hard-code the value at:
https://github.com/tomochain/tomochain/blob/ef51d97af0f58ef566beae958fe9d34bfe19a6c1/tomox/mongodb.go#L35

So we should add more params for tomo command to custom the value.
--tomox.mongodb.name default value tomodex
--tomox.mongodb.url default value mongodb://localhost:27017

[thanhnguyennguyen]

close as merging #687