Add data store interface and default implementations
Merge branch 'datastore'
Add getDataStore() method to XProcRuntime
Read http data and documents using the runtime httpclient and datastore
Use runtime httpclient/datastore for xinclude and other library steps
Support zip, css, and properties files over runtime httpclient/datastore
Remove unused getFile method
Use runtime datastore for fileutils to support virtual file systems
Merge branch 'datastore'