fileupload dependency bump, with FileItemHeaders-support

Mostly to shut sbt up about conflicting dependencies in a project I'm working on. 
I took the liberty of removing two casts which i couldn't understand the purpose of as well.

(I think all the tests still run green, on os x they don't shutdown cleanly)
This is just a style thing, but I'm becoming more of a fan of keeping imports at the top of files where I can see the file's dependencies laid out in one place. In the last refactoring of the netty modules I found tons of duplicated and sometimes unused imports in files. There are only a few cases where narrowly scoped imports are useful, implicit for instance. You certainly don't have to clean the imports up in this file for this particular pr but it might be a good opportunity do so since some of the imports changed.