Watch a key prefix and automatically pull changes into kvexpress format.

[darron]

I want kvexpress to be able to:

1. Watch a key prefix in Consul.
2. See the changes that are made.
3. Grab those changes and convert the value into kvexpress format - inserting it into the kvexpress destination prefix.

This way, for simple files that are a 1 to 1 mapping and don't require any variable substitution, we don't need to involve Consul Template into the mix.

This would save us a ton of configuration for each file that just ends up being boilerplate.

[darron]

I've been idling on this for a little while - had a chance this week to make some progress on this branch:

https://github.com/DataDog/kvexpress/tree/darron/kvexpress-watcher

It's acquiring and releasing Consul locks now:

http://shared.froese.org/2016/qkznu-11-39.mp4

Next steps:

• [ ] Set the watch on the prefix.
• [ ] Figure out what data is already there so that changes can be detected.
• [ ] See a change and insert the changed data into the new key.