Hi!

First of all excuse me for inconvenience. I failed my previous PR(#1187) branch during rebasing, so PR automatically were closed.

Briefly, PR about the same, feature #1133, and taking into account @nejch 's suggestion from (#1187)
Here I propose to introduce new custom managers ProjectMemberAllManager (/projects/:id/members/all/:user_id) and GroupMemberAllManager (/groups/:id/members/all/:user_id). Subsequently, in order to fetch a list or instance of members including inherited ones, you will need to:

project = gl.projects.get(project_id)
project.members_all.list()
project.members_all.get(member_id)
group = gl.groups.get(group_id)
group.members_all.list()
group.members_all.get(member_id)

@JacobHenner , just fyi.

Closes #1133