Improve Makernote support

[drewnoakes]

There are a lot of different makernote tags out there. Many are documented online:

• http://owl.phy.queensu.ca/~phil/exiftool/makernote_types.html
• http://www.ozhiker.com/electronics/pjmt/jpeg_info/makernotes.html
• http://gvsoft.homedns.org/exif/

Hand-coding classes for all of these formats may not be the best approach. Some analysis could be done to see whether this could be data-driven (say from an XML file, for example), either at runtime or design time via codegen.

Adding support for these makernotes is quite easy, and a great place to get started if you want to contribute to this library.

(Migrated from Google Code issue 8)