More complete support for signed operations

[mkorbel1]

Motivation

Right now most operations in ROHD are unsigned. Less than, greater than, etc. would be a lot more convenient with some built in signed support.

Desired solution

Allow operations to be performed using signed or unsigned math optionally.

Alternatives considered

Letting users do their own signed math is unnecessary overhead.

[mkorbel1]

Needs extensive testing as well, obviously

[mkorbel1]

This also needs to consider things like toInt and toBigInt for LogicValue. Currently, if you have a 64-bit LogicValue, then the resulting toInt is signed, but if it's less then that it won't be signed because upper bits are zero. A consistent solution should be provided for all sign-related features, including these functions.

[samimia-swks]

I imagine this is a pre-requisite to https://github.com/intel/rohd/issues/470