A project needs to be able to specify that it depends on a project
including extras for that project and still have it's version maintained
by global-requirements.
Currently if the requirements are seen to mismatch then the string from
global requirements is dropped in place of the project string, but this
drops any extras specified by project.
In the case that extras are different and the version needs updating add
a new combined requirement to the project with the original extras and
the new version.
Closes-Bug: #1567809
Change-Id: Ife48b7963a5e6706289f1b9a47cb95fae7f0bc22