Prior to this commit, the tumbler algorithm assumed that destination
mixdepths of INTERNAL transactions were incremented by 1, but the
underlying taker code uses (mod maxmixdepth) logic always. This commit
takes the decision to make the usage of the wallet "purely" cyclic, that
is, not only the Taker object but also the tumbler algorithm now always
treat the wallet as a cycle. This is not problematic in a tumbler
algorith (or any other schedule generation algorithm), as long as we use
the strict rule of "always exit each mixdepth with a sweep", which the
tumbler always did and this commit does not change.
Also, and importantly, several much more detailed tests of the tumbler
schedule generation have been added.
Adam Gibson