General feedback about the docs

[stefanodavid]

Does your feedback relate to a specific page? If yes, please add the link here.

http://opendatahub.readthedocs.io/en/latest/intro.html https://opendatahub.readthedocs.io/en/latest/involved.html https://docs.opendatahub.bz.it/en/latest/involved.html#roles-and-tasks new pages that will appear as result of the changes below

Your feedback

• [x] reorder general index, according to the proposal
• [x] dedicated point for Accessing data in the Open Data Hub
• [x] replace dropdowns of accessing method, replace with heading
• [x] rename "Roles and Tasks" in "How to access"
• [x] reduce size of images [add a :scale: option so they can open at full size]
• [x] reduce text width (currently set to 100% width, make it fixed 1024 points)
• [x] in source code boxes always use 'ready-to-go' examples, that can be copied and used for testing and modified (there should be few cases outside the Howto sectionm but check nonetheless)

[stefanodavid]

A couple of the code lines in the code blocks were not replaced because they are command that depend on the actual set up of the user (e.g., the name of a conflicting branch)