add context.chunkId and context.eof to onBeforeUpload

[menelike]

This adds chunkId and eof as context for onBeforeUpload to help solving #79

This is needed to determine if validation based on meta should fire. We need to know when to expect metadata since metais transmitted on the first and last chunk only.

[dr-dimitru]

We also need to pass the chunkId and eof to onBeforeUpload on the client to meet isomorphicity.

[menelike]

just to get this straight, your are talking about

https://github.com/VeliovGroup/Meteor-Files/blob/1953070657cc62ef033220faaa8106b8d7de822f/files.coffee#l1121
and
https://github.com/VeliovGroup/Meteor-Files/blob/1953070657cc62ef033220faaa8106b8d7de822f/files.coffee#l1126

right?
So eof is always falseand chunkId would be -1? Both static?

[dr-dimitru]

You're right, then we need to emphasise what this properties is Server only

[menelike]

I updated the docs, hope this fits now.

[dr-dimitru]

Great, thank you. Merged