Add address space model (chunk and reference)

[emesare]

We need to describe an address space for us to talk about things like symbols independent of Function instances.

To describe this we need to create a new chunk type containing a list of address spaces. Each address space will:

• Used to describe segments and the containing data
• Address spaces can refer to other address spaces and be treated as "mapping"s over one
• No concept of sections or segments, those are simply address spaces that point to another address space with a mapping.
• We will use this to back the file in the future
• Needs to handle multiple files easily

Might also want a way to "flatten" the spaces to talk about region permissions.