feat: made some methods of DdlDiff and DatabaseDefinition public so that it can be invoked within a Java application.

[gurminder71]

Currently the JAR can be invoked from command line via main method.

We are writing a service where during CI and CD phases the DDL diff need to be generated. So we need a programatic way of invoking the diff functionality from Java service where DDL files can be passed as strings instead of temporarily creating files on build system and invoking the JAR via command line.

There was a typo in DatbaseDefinition which has been refactored to DatabaseDefinition