Rewards for file upload should be rounded up to 64Kb chunks.

[Sriep]

Currently, we can have file uploads of around 1KB that are too small to trigger a payment. Hence rewards for file upload should be rounded up to 64Kb chunks.

commitBlobberConnection should have the size field in the input WriteMarker converted to multiples of 64KB.

Positive values of size round up to the next multiple of 64KB, negative values round down to the previous multiple of 64KB.

Return an error if the size is zero. Might need to confirm there is no valid reason for a zero size.