Add access to janusgraph-cla group for all PMC members

[porunov]

Right now this issue can be resolved only by @mbrukman .

There is a discussion to automate CLA signing. Right now there is a problem that CLA verification takes too much time (about 1 month). @pluradj suggested to give access to all PMC members but he couldn't because only @mbrukman has this authority.
@mbrukman You would help very much if you could give access to janusgraph-cla group to all PMC members. It would speed up CLA verification very much.
Please, tell if there is any concerns with giving this access to other PMC members.