RFE: Initial volume of Gluster in GCS

[amarts]

We should go with replica 3 (1x3) volume type, and below config in my opinion in GCS. We will start with bare-minimum volume options, and then add features along the way.

For mvp0:

Brick Graph:

posix
access-control
locks
upcall
io-threads
selinux # do we need it?
index
io-stats
server

Client graph: (Goal, all applications should run, performance next).

client
replica
dht
io-stats

I will start another issue with Options available in each of these translators, and we have to agree to the default options on each of these.

@gluster/gluster-all

[atinmu]

Default template of the volfiles can be found at https://github.com/gluster/glusterd2/blob/master/glusterd2/volgen/defaults.go#L47 .

[amarts]

@nbalacha @raghavendrahg @xhernandez