Support Reference Types

[skas102]

The existing virtual machine work with value types for all types including arrays, maps and structs. This should be changed due to various reason such as gas cost (which are currently really high -> See Array Opcode ArrAt) and space efficiency.

In this issue we should find out, what changes in the vm would be required to be able to support reference types.

Things to concider:

• A simple heap implementation might be required to map the references to pointers.
• How is the garbage collection done? Is it required?
• Are there OpCodes that need to be created/removed/modified?
• Is the Roll Opcode still required? Could it be an alternative for the heap?
• Other ideas on how to solve this issue.