Use Hadoop CredentialProvider API to encyrpt passwords at rest

HADOOP-10607 introduces an API to isolate password Storage from applications. This can be used to provide the DB password in a secure fashion to Sqoop users.

The DB passwords can be assigned an alias and stored in a keystore and the alias can be provided to Sqoop.
Option to provide the password on the command line (using --password-alias) option can be introduced as well as enhance the secure file option that we currently have to provide a new password loader that resolves the alias from keystore.

We need to detect the availability of the Credential Provider feature and use it and fail gracefully otherwise