FileFormat does not support multiple extensions

[charliettaylor]

Some file formats have multiple extensions and it would be nice to be able to have aliases for them. For example, image/jpeg can be .jpg or .jpeg and image/tiff can be .tif or .tiff.

Suggested change:

• Add a new property to FileFormat called something like Extensions or OtherExtensions
• Update constructors to allow an optional list/array of alternate extensions to be passed