Consistent, namespaced definitions for office file related metadata

Currently, we have the MSOffice metadata definitions, which is a mixture of Properties and Strings, none of them namespaced. Despite the name, the keys apply to a wide range of Office Documents (not just MS ones), and the keys are taken from a mixture of sources.

Similar to TIKA-925 / TIKA-928, we should replace these with prefixed versions drawn from a few well known externally defined namespaces, then deprecate the old ones.