Update README, only announce features that are acutally provided

[dariok]

README announces ocrd-segment-via-template and ocrd-segment-via-model – none of which are actually provided by this package.
It does provide some ocrd-segment-extract-* features; these do not do any segmentation though (or I could not find out how).

[kba]

Keep in mind that this is not an official OCR-D project, but a side project by @wrznr and @bertsky. Which does not mean that it wasn't great software (it is!) just that documentation and support won't be as much of a priority as for official projects.

That being said, the ocrd-tool.json is the best way to understand which processors come with a project, their parameters etc.

[bertsky]

Thanks, I just updated the README anyway.

[dariok]

@kba True, but the first thing someone sees when going to github to clone the repo is the content of README – as I came here via gitbub.co/OCR-D, I only noticed that after cloning.

@bertsky thanks!