Changed mime type map to deal with the reality that certain file types have multiple extensions and/or multiple mime types, as well as constants supporting all of the data. Created new functions using the updated mime type map to resolve mime types and extensions. Updated various items around the project that determine mime/extension to take advantage of the new functions.
Added new event to handle fetching media properties like height, width, and the newly added fields, and admin controls to manually scan files for their properties.
Added a search terms content:video and content:audio to search for images that do (or do not) have those flags.
Bug fixes and consolidation of various thumbnail and resize functionality
Changed resize/rotate extensions to use replace image event
Added content-disposition header to image responses to provide a human-friendly filename when saving
Added more bulk thumbnail regeneration tools
Tweaks to bulk actions to correct totals when batching items
