#48 Support analog display for digital vectors

[Matthew Ballance]

Support for graphing the analog representation of a
digital signal can be very useful for a developer
working with a DSP design.

Effectively, IVI would need the following changes
to support graphing digital signals as an analog quantity
- fully-configurable trace height. The user will
probably wish to make the analog traces 2x, 4x, or 8x
the size of a regular digital trace
- support for common analog data formats
- unsigned
- two's-complement