Given a nested list of integers, returns the sum of all integers in the list weighted by their depth
For example, given the list {{1,1},2,{1,1}} the function should return 10 (four 1's at depth 2, one *2 at depth 1)
Given the list {1,{4,{6}}} the function should return 27 (one 1 at depth 1, one 4 at depth 2, and *one 6 at depth 3)