Move binary assets out of git

Fixes #32

The res directory has been removed. The directories res/scripts and
res/ogre_cfg have been moved up into the root directory.

CMake now offers an option to set the asset directory and throws an
error if it doesn't exist or is empty.

Asset creators can now put their files in the "testing" subdirectory of
an installation to override any other resource files.

Move scripts up one directory

Remove binary assets from git

Add "testing" resource directory

The content of this directory overrides all other resource
directories.

Move res/ogre_cfg to ./ogre_cfg

Let's get rid of that res directory

Remove unused music file

Will be added to the asset repository later

Remove res directory

The Blender files have been moved to the asset repository

Fix SVN URL in CMake warning

Add username / password hint to CMake asset warning

Promote CMake asset warning to an error

In theory, users could build Thrive without assets, but it
wouldn't do them any good because there's no way they could
execute it.

Better README.md

Add simple explanation for Subversion art asset

Add dependency list for Linux developers

Attempt to fix links

Write out ftp link since GitHub seems to filter them