Allow GET Recording Downloads & PUT

During our usages of kapacitor there has been a constant requests of having a base set of recorded training 'sets'.

We were hoping to be able to record known situations and provide it to different team's kapacitors that are running in their own docker containers.

The issue does not identify files, tests, or an entry point. First trace Kapacitor's recording functionality and existing HTTP API, then define GET and PUT behavior for sharing recorded training sets across Docker containers. Done requires an agreed request/response and persistence scope, with tests covering the behavior.

Written by the indexing model from the issue text.