Fix more of the cookie test following API changes.
App Kit: style changes.

No functional change intended.

Focused on documented classes only.

* Update copyright information.
* whitespace fixes.
* pointer style
* Rename some variables, msg => message, form => what
* Need consistent variable names to make documentation easier,
  allows us to use \copydoc or \copydetails instead of repeating
  ourselves over and over again.
Add styling for \since command
Update App Kit Documentation.

The biggest change is the addition of \since to each method. I've gone
through old versions of the BeBook and documented what version of BeOS
each method was introduced in. I'm only counting production releases
so I'm starting with BeOS R3 ignoring all DR and PR releases. Likewise,
all methods new to Haiku are listed as being introduced \since Haiku R1
ignoring alpha releases.