Read schema from file

[ksuderman]

If no schema is specified on the command line then the $schema field in the instance should be used. Throw an exception if neither is specified. A schema specified on the command line should take precedence over the $schema field.

[ksuderman]

The $schema field will be required in the 1.1.0 schemata and support for it will be added to the next version of the LAPPS Grid Java API.