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.
Thumbnails will only be good if they can be linked to a full-size image, which is something I would hope I can do in ReST, but I'll have to check the Sphinx docs on that. They're already full-size in-page, to the extent of being displayed at the full width of their container.