Added a beforeall event with files and a filelimit.

Filelimit is there so you can set the amount of uploads at a time, for example if you want to limit it to just 1.
The before all event is there so you can do something with the uploaded files before the start of uploading.
Allow operations on XMLHttpRequest before send()
Fixes #514
Fixes #497
marked updated
Fixes #522
Merge pull request #507 from windvlaag/master

Added a beforeall event with files and a filelimit.
cleanup
Fixes #469
jquery updated to 2.1.1
Fixes #503
Merge pull request #516 from regisf/allow-xhr-operation-before-send

Allow operations on XMLHttpRequest before send()
cleanup
Fixes #485
overview: added simple item to navbar