Add --database flag to sqlcmd query

[stuartpa]

This closes #287

For sqlcmd create scenario the default_database is set on the user login (in the master database attached to the sqlserver in the container). This means the default_database isn't stored in the sqlconfig file. (this also means we don't have to deal with this value getting out-of-sync between the sqlconfig file and the container instance)

However, a user might delete their default database, which then prevents connecting without specifying a different database (master), to change the default database (this PR also added a # Example on how to do this)

The user might also just want to query a non-default database.

With this PR the user can do

sqlcmd query "PRINT DB_NAME" --database some-other-database

[shueybubbles]

  	endpoint.EndpointDetails.Address,

is there no way to put the database name in the endpoint in the config?

How does this path implement the hierarchy of command line switch -> environment variable -> config file?

---

In reply to: 1458373819

---

Refers to: internal/sql/mssql.go:37 in f632d34. [](commit_id = f632d34, deletion_comment = False)

[stuartpa]

  	endpoint.EndpointDetails.Address,

I've added an issue to enable database name to be added to sqlconfig file

#297

---

In reply to: 1458373819

---

Refers to: internal/sql/mssql.go:37 in f632d34. [](commit_id = f632d34, deletion_comment = False)