Clean up and simplify metadata form subclassing
Make mouse tracking publicly available

...as multiple forms need access to it
Remove custom mouse tracking code from MDI child forms

see previous commit
New comprehensive collection of photo filters

Effects -> Stylize -> Photo Filters

To my knowledge, this is the most complete digital collection of classic
Wratten filters.  I have pieced together this list over several months
from a huge variety of sources - see code for a complete list.

The longest part of implementing this was the custom form required to
display complex list items.  Rather than do an owner-drawn combo box (a
technique with a variety of problems), I built my own form from scratch
using ideas first implemented in my Metadata Browser and About dialog.
The resulting form is clean and modern, and it allows complex list text
to appear alongside colored boxes, with full support for hover and
clicking.