ruby: Remove RubyMemoryControl and associated files

This patch removes the deprecated RubyMemoryControl. The DRAMCtrl
module should be used instead.

ruby: Move Rubys cache class from Cache.py to RubyCache.py

This patch serves to avoid name clashes with the classic cache. For
some reason having two 'SimObject' files with the same name creates
problems.

ruby: initialize replacement policies with their own simobjs

this is in preparation for other replacement policies that take additional
parameters.

ruby: interface with classic memory controller
This patch is the final in the series. The whole series and this patch in
particular were written with the aim of interfacing ruby's directory controller
with the memory controller in the classic memory system. This is being done
since ruby's memory controller has not being kept up to date with the changes
going on in DRAMs. Classic's memory controller is more up to date and
supports multiple different types of DRAM. This also brings classic and
ruby ever more close. The patch also changes ruby's memory controller to
expose the same interface.

ruby: remove sparse memory.
In my opinion, it creates needless complications in rest of the code.
Also, this structure hinders the move towards common set of code for
physical memory controllers.

ruby: move files from ruby/system to ruby/structures

The directory ruby/system is crowded and unorganized. Hence, the files the
hold actual physical structures, are being moved to the directory
ruby/structures. This includes Cache Memory, Directory Memory,
Memory Controller, Wire Buffer, TBE Table, Perfect Cache Memory, Timer Table,
Bank Array.

The directory ruby/systems has the glue code that holds these structures
together.

ruby: add a prefetcher
This patch adds a prefetcher for the ruby memory system. The prefetcher
is based on a prefetcher implemented by others (well, I don't know
who wrote the original). The prefetcher does stride-based prefetching,
both unit and non-unit. It obseves the misses in the cache and trains on
these. After the training period is over, the prefetcher starts issuing
prefetch requests to the controller.