Need mlcp to not ignore files in folders starting with underscore

[janmichaelyu]

When migrating a project built on app-builder that uses templates for creating Excel documents, the code requires files in the content db with the following structure:

- <sheet name>
    - docProps
    - _rels
       - rels.xml
    - _word
       - _rels
         - document.xml.rels.xml
         - ...
    - [Content_Types].xml

The workaround detailed in https://github.com/marklogic/marklogic-contentpump/issues/87 doesn't apply since we need to preserve the structure.