Use safe keyword when hook target namspace clashes with reserved java…

[Brianwithay21]

… keywords

Issue #, if available:

Description of changes:
Using a safe keyword that appends a _ to the end of a nampspace if it is a reservered keyword in Java. This is updated for when generating POJOs for a Resource Hooks targets.

For example, the AWS::Panorama::Package resource was generating the following path:

package com.mycompany.testing.mytesthook.model.aws.panorama.package;

public class AwsPanoramaPackage extends ResourceHookTarget {

...

}

------

public class AwsPanoramaPackageTargetModel extends ResourceHookTargetModel<AwsPanoramaPackage> {

...

}

Now a underscore is added so there is no name clashing causing complication errors for these certain resource types:

package com.mycompany.testing.mytesthook.model.aws.panorama.package_;

...

public class AwsPanoramaPackage_ extends ResourceHookTarget {

...

}

-----

public class AwsPanoramaPackage_TargetModel extends ResourceHookTargetModel<AwsPanoramaPackage_> {

...

}

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[mrinaudo-aws]

LGTM