couchbase-cli: Add support for collections

Add support for collections:
Top level command will be: couchbase-cli collection-manage

There will be a flag to say which bucket the action should be taken against

--bucket [bucket]

Then the flags will be:

--create-scope [scope]
--delete-scope [scope]

The flag will take the name of the scope

--create-collection [scope.collection]/[collection]
--delete-collection [scope.collection]/[collection]

The flag will take a path like argument scope.collection.

--list-scopes

The flag will not take an argument and will list all the scopes in the bucket

--list-collections [scope]

The flag will take the scope, if none is provided it will use the default scope

The create collection will accept --max-ttl to set the max TTL.

The REST API spec is explained here:

https://github.com/couchbase/ns_server/commit/4c1a9ea20fbdb148f68ec2ad7be9eed4c071bf9e

It should be noted that this spec is not set in stone