Implement :On error [exit | ignore] command

[apoorvdeshmukh]

go-sqlcmd currently does not have support for :on error command.

:On Error[ exit | ignore]
Sets the action to be performed when an error occurs during script or batch execution.
When the exit option is used, sqlcmd exits with the appropriate error value.
When the ignore option is used, sqlcmd ignores the error and continues executing the batch or script. By default, an error message is printed.

[apoorvdeshmukh]

Can be closed as #166 #181 #192 addressed this.