Add `cutoff_length` as a property to `Analyzer`

[dennlinger]

Currently, only a single function (Analyzer.detect_leakage) supports the cutoff, which greatly reduces output bloat for "print-to-console" functions. A better solution would simply be to define this as a cutoff on the class level, which can then be utilized across multiple functions with minimal additional effort.

[dennlinger]

Importantly, I realized that setting cutoff_length to None by default will produce a consistent result (i.e., output the full sample unless a cutoff is specified).

x = [1,2,3]
print(x[:None])  # will output [1,2,3]

[dennlinger]

Added with #38