Allow DATABASE_URL to be provided

[naude-r]

would it be possible to allow an optional DATABASE_URL to be provide? this is mostly to configure jdbc url that differs slightly from the norm, e.g. mssql:
jdbc:sqlserver://localhost:1433;DatabaseName=hive_metastore;

using the existing env variables result in an error:
Underlying cause: com.microsoft.sqlserver.jdbc.SQLServerException : The port number 1433/hive_metastore is not valid.

if DATABASE_URL is specified then the other connection related env can be skipped.