Move out duplicated content into shared include

This starts the process of refactoring the samples to not be inline.
Instead, this change creates a solution that the samples are added to in
order to validate they are correct (and enable refactoring much easier
in the future). This adds a script in the samples directory that helps
scaffold out a new sample project.

docs/open-xml-docs is where the docfx build ends up - it appears to have out of date assets that are overwritten with the build. This change removes the directory and adds it to .gitignore

As part of this change, a default template is added to docfx.json so that local builds can work.

Add docs output directory to .gitignore

Add samples projects to a solution