Draft: Add virtual memory

This change would introduce virtual memory in the kernel in a style similar (and inspired from) the Linux kernels implementation.

The issue of global symbols as referenced in #7 is overcome by jumping to a fixed place in virtual memory given by a constant rather than using a global symbol. The default for this fixed virtual address is chosen as the max jump into high memory by the JALR instruction (-2GiB from 0).

This change also includes many other changes made while adjusting the code for virtual memory.

I propose that when merged, the version be bumped to 0.1.0.