Upload progress

[ramiresviana]

This new upload progress calculation fixes the following issues:

Non linear progress

• On a batch of multiples files, the progress bar increases faster when is uploading a small file. The progress should increase linearly, based on size of all files being updated.

Inconsistently progress #990

• Every time user uploads a file, a new calculation is made based on the current batch of files, ignoring files that was being uploaded before. Calculation should be done with information of all files being upload.

Performance

• Events from files being uploaded can be heavily expensive, every upload will trigger multiple events every second. Using throttle is possible to limit the execution of some functions.