tests: integration: set restriction_caps on the video encoding profile

We need this cause now videomixer renegotiates downstream.
ges-pipeline: Don't unref buffer obtained from a GstSample

https://bugzilla.gnome.org/show_bug.cgi?id=707914
ges-launch: Make it possible to provid pathes to look for moved asset

For example if a project was sent from someone else thus the pates in
there are meaningless on the other computer, we need to be able
to specify a list of pathes where the files are.

+ Fix documentation
formatter: Keep timeline duration as a meta
ges-launch: Handle path for project uri
tests: timelineedition: cast start and duration values as guint64
docs: add proxy editing design
tests: add proxy editing test
project: add proxy editing
project: some fixes
project: add pause proxy creation
docs: add progress API in proxy editing design
docs: add uri API in proxy editing design
project: add API for get proxy state
project: fix pause proxy creation
docs: small fix in proxy edition design
project: add API for setting user location in proxy editing
docs: added allow-none annotation
project: create proxies one by one
project: creating one by one, start implementing GCancellable