Specify document properties when loading files

[rjrudin]

https://github.com/marklogic-community/ml-javaclient-util/wiki/Loading-files describes how to specify collections and permissions when loading files. Should be able to specify document properties as well... and possibly document metadata and document quality too. Specifying document properties would be useful for the ML Java Client project, as it needs to include document properties on several of the files it loads for testing purposes. Actually - the Java Client project didn't really need this for its tests, but this may still be a useful feature.