Store dates as integers to keep the server precision

Current state

1. Dates are returned from the server as integers representing a Unix timestamp (lastModificationDate for instance). It contains milliseconds precision.
2. On the client side, those dates are rounded to the second and thus we lose a small, but precious, precision.

Why bother with milliseconds?

Before NXDRIVE-175, an audit event was filtered out if last modification dates were the same. And it was smart. But as seen in NXDRIVE-175, without millisecond precision, there are issues.

I would like to investigate if we can store dates in the database without loosing the milliseconds precision and restore the simple check in the Remote Watcher. That would be a small optimization, yet interesting.

It would also help fixing issues when the document digest loses its meaning (like when transferring files using S3 + SSE-KMS). Currently, Drive thinks that the blob has changed, but it is just a value set from S3 that does not help checking blob integrity. Working around the issue is doable, but it is not clean.