Adding getCheckedPointerParam

[andrsd]

1. Added getCheckedPointerParam to MooseObject
2. Used the method in framework to make the code more robust

Closes #10356

[moosebuild]

Job Precheck on 4f6f297 wanted to post the following:

Your code requires style changes.
In the top level of your repository, you can run:

git clang-format 0315ecc2c5616eddb269a70e4f95a97c3f9efb14

Alternatively, apply the patch found here.
You can directly apply the patch by running, in the top level of your repository:

curl -s http://mooseframework.org/docs/PRs/10358/style.patch | git apply -v

[moosebuild]

Job Documentation on 3ba3378 wanted to post the following:

View the site here

This comment will be updated on new commits.