Added an internal plugin for changing a plugin's format metadata
The plugin allows users to set a file's mimetype, PRONOM identifier, format designation, and format version
Files altered with this plugin are given the "manual" note in their PREMIS file format note
SiegfriedPlugin now has a parameter, set to false by omission, that needs to be set to true in order to overwrite format data on files whose PREMIS format metadata was manually edited
Items processed by SiegfriedPlugin that were not altered because of this parameter are marked as Skipped