Support for O(n^k) algorithms.

jFit currently supports quadratic time $O(n^2)$ algorithms only. This issue proposes extending support to cubic, quartic, and potentially all 1D array algorithms in class $P$.

Start by reviewing how jFit currently represents and plots quadratic O(n^2) algorithms. Determine the intended scope for cubic, quartic, and broader 1D polynomial-time algorithms, then define completion against that scope; the issue names no files or tests.

Written by the indexing model from the issue text.