Style guide: incremental find as you type in widgets

Comments on the inclusion of incremental find as you type in the style 
guide:

1. Only the tree view mentions "Typing a letter key moves focus to the 
next instance of a visible node whose title begins with that letter. ". 
Combobox, menu, popup menu and listbox should also have this.
2. This should say "printable character" which meas a letter, number, 
space or punctuation. It's important to be able to use any of these 
characters, although for space it may only be supported after the first 
character if it's needed for toggling (e.g. in a tree item checkbox)
3. For everything but menu, typing more than 1 character should allow 
searching to the first item that matches the total substring. Moving with 
another key cancels out the current string.
4. However, typing the same character multiple times often goes to the nth 
item starting with that letter. This is not as usually considered as 
important as item #3

- Aaron