introduce qt.deps_branch property
introduce qt.deps_branch property

this allows setting a different default branch for the tested repo's
dependencies. this is useful for feature branches which typically exist
only in one repo.

Change-Id: Id63570900cd141e4f24aa2f23a1f4c0f5dc13a8a
Reviewed-by: Tony Sarajärvi <9f5d03eac1d5fa677086d4fb7148df11e4536984@digia.com>

tsarajar/qtqa,tsarajar/qtqa,tsarajar/qtqa,tsarajar/qtqa