Enable engine=postgres in gorm_out

[fi0]

what're your thoughts on enabling engine=postgres in the gorm_out configuration?

[Calebjh]

Hmm. The specification here https://github.com/infobloxopen/atlas-cli/blob/master/README.md#flags actually does specify "Postgres", so it seems like it makes sense to me (until/unless that is changed to include other DBs) to include the engine=postgres clause. @razamiDev?

[razamiDev]

At the moment, by default we use the postgres database.
Currently we don't have any plans on using anything other than postgres, if we see lots of interest in other engines then we can definitely look at options.