cli: add scrolling to repo register, fix --repo and update the cli docs

[rdimitrov]

The following PR adds a bit of polishing to the medic cli -

• Removed the paging while doing repo register. It now lets you have 20 items per screen but you can scroll dynamically through your full list of repos for a better UX.
• The --repo flag is now working
• Went through the flag and command descriptions for each call and fixed things to be consistent across the whole CLI
• Regenerated the cli docs

Fixes: #861

[lukehinds]

A lot of this is about to be stripped out