Add scylla connector

[dkropachev]

It is essentially copy of cassandra connector.
Only two options added:

1. Consistency level
2. Host policy config

Since github.com/scylladb/gocql has github/gocql/gocql module name it is necessary to have go.mod in scylla connector directory with replace directive.

[CLAassistant]

All committers have signed the CLA.

[mihaitodor]

Thank you @dkropachev! I haven’t looked at the code in detail yet, but I was wondering if this issue scylladb/gocql#161 will get resolved soon to avoid having to maintain the go.mod replace directives.

[dkropachev]

Thank you @dkropachev! I haven’t looked at the code in detail yet, but I was wondering if this issue scylladb/gocql#161 will get resolved soon to avoid having to maintain the go.mod replace directives.

Unfortunately, it is going to be a long story, proper way to do that is to have next major release, which is going to take some time.
Also, it is going to be really easy to get rid of go.mod when scylladb/gocql finally get it's own package name.

[dkropachev]

@mihaitodor , ping