Provide an optimized partitioning for performance and space

Choosing the right storage drives is a game of balancing three different, competing needs:
- performance: I/O (read/write) speed.
- space (e.g. for large media files).
- reliability (permanent storage, backups).
Depending on the required amount of storage, and the amount of money available for spending, the right solution may be different.

However, our new distribution will strive to provide a sane default, with a judicious use of a /scratch partition: