Refactor: Organized core resources into packages

Added new packages:

- net.dengine.base: contains files shared by the client and server
- net.dengine.client: files for the client only
- net.dengine.stdlib: Doomsday Script standard library
- net.dengine.stdlib.gui: Optional GUI package for the std lib

These packages are loaded as "init" packages, meaning they will be
loaded by App immediately after the file system has been first
populated. This makes them available when the application configuration
is parsed (appconfig imported from Config).

The "deployPackages" macro can be used to easily deploy packages via
the app's .pro file.

With these new packages, it is no longer necessary to deploy the
individual .de scripts, help strings, and other files.

Note that the client's old "data/graphics" and "data/fonts" folders are
still untouched and accessed solely via FS1.

As a new feature, a package may now specify additional DS module
import folders using the 'importPath' metadata variable. The import
path is naturally effective only when the package is loaded.

The main DED file (doomsday.ded) is now loaded via FS2, explicitly
from the net.dengine.base package. Similarly, the help strings are
loaded from net.dengine.base by libdoomsday.