Should rename .OptionalPackageDescription to .PackageDescription

[umccullough]

It seems like the name .OptionalPackageDescription was a little too verbose for what it's used for.

I propose it be changed to something simpler such as .PackageDescription, as the current name almost makes it sound like the file itself is optional.

Looks like it would be simply to support either filename in the build system, and we could eventually phase the old one out.

However, if we plan to eliminate this file and go with a different meta info storage in the future, then it's probably not worth it I suppose.

[bonefish]

Implementing support for an alternative file name is trivial to implement. If anyone wants to do that, just go ahead.

Since we're pushing for actual package management, which very likely won't use this file format, I guess we'll eventually switch to the same package format for the optional packages. So no need to bother.

[scottmc]

As bonefish said, this would be easy to do, but there wouldn't be much gained and it'll be phased out soon anyways, so closing this out. Marking as invalid as there is no "won't fix" resolution on Haiku's trac.