No inline JS - Work in progress

**This is a work in progress - please don't merge**

Ok, there we go, as I stated in #620 I'd like to move all inline JS scripts to external files. This will be a *really huge* security improvement since it allows us to disable the execution of inline JS browser which "prevents" a lot of XSS. 

Compatible (checked) apps at the moment:
[x] files
[ ] files_encryption
[ ] files_external
[ ] files_sharing
[ ] files_versions
[ ] user_ldap
[ ] user_webdavauth

Feel free to add your app on this list and/or help in this branch :)

TODO: Add a PR on the apps repo.