Expose further settings in Cassandra image

[sunnychanwork]

We would like to expose these configuration settings which has been useful in our production environment

storage_port
ssl_storage_port
native_transport_port
rpc_port
read_request_timeout_in_ms
request_timeout_in_ms
range_request_timeout_in_ms
write_request_timeout_in_ms
counter_write_request_timeout_in_ms

[blop]

Is this actually implemented ?

[tianon]

No, see #41, #112