Establish convention for "connect data" plugins

[Bargs]

Back in the good old days of January I created a ticket for an "Add Data UI" #5974 (title now changed). The idea was that we would create a series of similarly structured wizards for adding data to Elasticsearch. A lot has changed in Kibana land since then. We now have a Management app instead of a Settings app, and Management has a dedicated section called Connect Data that any plugin can easily add a link to. At the same time, my work on Add Data has led me to believe that it's a mistake to think of "Add Data" as a monolithic project consisting of a number of highly similar wizards. A data adding UI could take many forms, some of which might share a few common angular directives, but that's it.

So instead of continuing to think of "Add Data" as one giant feature, I'd like to take a step back and establish a convention for creating "Connect Data" plugins, which at the moment is basically any plugin that adds a link to the Connect Data section in Management. To do that, I'll attempt to extract the "Existing Indices" and "CSV Upload" features out of the Kibana plugin and put them in their own separate plugins (but still within the Kibana repo). These new plugins will serve as examples for other contributors who want to create their own Connect Data UIs.

An added benefit to this mental shift is that other "Add Data wizards" can be thought of as their own standalone projects. A stall in work on the Tail a File wizard, for instance, will no longer block the development of other data adding plugins by anyone else on the team or from the community. Thinking of each data adding UI as a standalone feature (rather than a slightly modified cookie cutter wizard) should also lead to a better, more focused user experience for each unique workflow.

[chrisronline]

Closing this out. This idea is still valuable, but we've started moving in a different direction, specifically with a new home page