Streamline tutorial docs

Fixes #634 
Replaces repetitive tutorials with an "Examples" section in "Getting Started", with much simplified structure and tutorials replaced with more minimal example Flocker config files and instructions.
The way we have these examples structured is not ideal from a users perspective. We are mixing "feature" tutorials like using Links or Environment Variables, with "database specific" tutorials like the PostgreSQL tutorial.  

This means, that if a user comes looking for samples using ElasticSearch, they won't find it (at least not easily), because it is buried in the Linking tutorial.

I think that we should have 2 views on our samples, a "database" view, where we list samples by technology, and a "feature" view, where we highlight particular features. The content can stay more or less the sample, but the information architecture is different.