Fixed sorting in `list_proposal_votes` and exended tests

Issue: #81 (closed)

Descending sort skipped part of result (about 2-3 results), because of incorrect default values.

Here is example of bug:

For sorted collection: [ 1, 2, 3, 4, 4, 4, 5, 6, 7, 7, 9 ]
Sort: Ascending, Start: 4: [ 4, 4, 4, 5, 6, 7, 7, 9 ]
[BUG] Sort: Descending, Start: 4: [ 4, 3, 2, 1 ]
[FIX] Sort: Descending, Start: 4: [ 4, 4, 4, 3, 2, 1 ]

@bwrona @dan @Trela