feat(plugins) new Galileo plugin

[thibaultcha]

• Implement the ALF 1.1 specs from https://github.com/Mashape/api-log-format
• Implement the latest Galileo agents specs from https://github.com/Mashape/galileo-agent-spec
• Rename the plugin from mashape-analytics to galileo. This still requires more testing than I did so far
• It has more tests than the old plugin, and should perform better.

Still waiting on openresty/lua-cjson#6 to make it to an OpenResty release, until then, this still uses a workaround to serialize empty table to empty JSON arrays.

Goes with Kong/docs.konghq.com#214 for the updated documentation.

[subnetmarco]

As a reminder, if the target port is 443 this plugin should be able to handle HTTPs.

[thibaultcha]

Perfectly aware. Still waiting on Galileo v3 running in prod with SSL support.

[subnetmarco]

By the way I think the protocol should be specified in a separate property. I could have Galileo running on-prem on an arbitrary HTTPs port, like 9000, or running on port 443 but under HTTP.

[thibaultcha]

Also aware, also planning on doing it once Galileo v3 is released.