Client: Collected packages inside "net.dengine.client" package

All the stuff specific to the client is now inside "net.dengine.client".
libcore|FS: Order for packages, finding files in packages

While Package doesn't yet have a file index of its own, FileIndex can
now make searches in all loaded packages. The results are sorted to
be in the same order as the packages were loaded in.

Minor cleanup in the Record class wrt. removing members.
Client|Renderer: Load shaders in package order

Shader definitions are now loaded in package load order (although that
has no practical effect at the moment).