show mdui:DisplayName instead of md:OrganizationDisplayName

[peter-]

Currently DiscoJuice seems to show md:OrganizationDisplayName for IdPs, which makes it impossible to differentiate between seperate IdPs run by the same organization (e.g. ACOnet vs. ACOnet's OpenIdP). For suggested precedence see #47 or the mdui spec.

[martinhaase]

I'd like to vote for this issue being fixed soon. People send out foodl.org links, and quite a number of our DARIAH users would like to use it but do not know that our IdP happens to be run by the "Gesellschaft für wissenschaftliche Datenverarbeitung mbH".