[Feature Request]: External Sites, Add target Option

[Mannshoch]

iframe is out. I never got any site work with Iframe.
Pleas add Option for Open external. Please also prepare include posibility to work together with other website like wordpress or similar.

I Use Owncloud as Backend to control other tools. Would be nice to be able to show the wordpress backend in Owncloud.

[fxcb]

I've created a new pull request (#2216) related with this issue for the 9.1 version