Added quota information

I’ve added quota support information to the Linux Sea book as well as information about the eclean command for cleaning distfiles and packages. The part on building a Linux kernel has been moved into its own chapter, the chapter on hardware support now has a bit more information about dealing with sound cards (ALSA support) and will contain information about sound servers in the near future. This chapter will also be used to configure the various other hardware things as they come by (printers, scanners, …).