I have experience with pootle, and believe me, the format is your last concern. There are a lot of command line tools to do any kind of conversion, but using them correctly and automating pootle behind the scenes is a bit more involved.
The easiest one to deploy and use would be Transifex, the interface is really nice and the support for Qt translation files is great.
I have been playing with it here https://www.transifex.com/nu-network/desktop-wallet and is up and running on 5 minutes.