Additional methods for cyclic register generation

[bobbinth]

Right now, 3 methods are available for specifying values for cyclic registers:

1. Explicit list of values
2. prng expression
3. power expression

A few other methods would enable succinct definition of more elaborate value patterns:

1. Patterned expressions, for example; (repeat 1 4) (repeat 0 4) instead of 1 1 1 1 0 0 0 0
2. Function calls where repeated invocation of a function would define the sequence of values.
   a. This can be expanded into generating values for multiple registers at the same time.
   b. This can potentially replace power expression - though, maybe having a simple way to generate a power sequence is still a good idea.