Consider dropping last odd numbered checkpoint

[ccjernigan]

STEPS TO REPRODUCE

1. Run the command python3 checkmate.py mainnet.lightwalletd.com:9067 --start-height 1650000 --to-json
2. Look at the output files

RESULTS

Actual

The final checkpoint is not an increment of 10000.

Expected

When generating checkpoints, one provides a starting height and expects checkpoints to be emitted in intervals of 10000. The final checkpoint should probably also follow the 10000 convention.

NOTES

The reason to consider implementing this is to reduce the introduction of odd-numbered checkpoints into the iOS and Android SDKs, as often the person generating the checkpoints will just drag-and-drop the outputs of this script into the SDK and not drop the last checkpoint.