Issue583docs4displaynamesAndDeleting

Docs for ref #318 (use display names table to delete unwanted studies) and ref #580 which is about better handling of RDSR from fluoro or DX.

As before, any comments welcome. I'll merge it in otherwise tomorrow.

Docs at

• http://docs.openrem.org/en/issue583docs4displaynamesanddeleting/i_deletestudies.html and

• http://docs.openrem.org/en/issue583docs4displaynamesanddeleting/i_displaynames.html