Improvements to the docker build script

[cticenhour]

With these changes the Dockerfile doesn't need to be updated manually. This is in preparation for a staged move to

1. Automating MOOSE submodule updates from CIVET instead of dependabot, and then
2. Automating the Docker build process through Docker Hub directly now that shannonlab is a proper Docker Team.

This PR also moves the Dockerfile to the scripts directory. It's not necessary to keep it in the root directory, so let's place it beside the script that actually uses it.

Refs #155

[cticenhour]

Also adding a dependabot config update in 3014bf4 to go ahead and remove moose from submodule updates through that method.

[cticenhour]

Docker precheck requirement has been removed from CIVET as of idaholab/civet_recipes#1217

[moosebuild]

Job Documentation on 12ee59c wanted to post the following:

View the site here

This comment will be updated on new commits.

[cticenhour]

@csdechant can you give this a review? Going to kick-off automated updates through CIVET after this makes it to the master branch.

[cticenhour]

Thanks!