Add deterministic upload mode

[glasser]

This is to avoid #600.

In this mode, decisions about whether to upload files are only based on
properties of the input messages themselves: timestamps and input message
payload size. We don't care about real-world time, disk file timestamps, or log
file size; we don't support upload on shutdown; and we check for uploads after
every message.

Configuration:

• set secor.upload.deterministic=true
• Configure at least one of secor.max.file.timestamp.range.millis and
  secor.max.input.payload.size.bytes.
• If you've configured secor.max.file.timestamp.range.millis, you must
  set kafka.useTimestamp=true and ensure that your FileReader/FileWriter
  supports timestamps.

[glasser]

I don't know if this fix is good to be upstreamed or if it's what the project wants, but it's what we're going to try for our installation.

[HenryCaiHaiying]

Looks good to me. I will merge in this PR, it's a good fix for secor.

[jeremyplichtafc]

@glasser - I was reading your code and trying to understand something. If deterministic mode only looks at the time difference in the message for that partition and the size of input for that partition wont you have the case where a partition only gets a handful of messages (never triggering the time or size criteria) and is never uploaded? Especially if you are splitting them up into smaller partitions using SplitByFieldMessageParter.

[glasser]

That's probably correct, and should be mentioned in the docs for the option — open a PR?