Accounts handling in Plasma 5

[David Edmundson]

> Then there's the fact that this makes KTp hard-depend on the Accounts-SSO framework starting with frameworks

I'm not particularly comfortable with this.

If it becomes a major component of workspace adopted by all with all
relevant parts are all merged properly into workspace/extragear, all
should be OK.

If this ends up with KTp depending on some unmerged playground repos,
I will be really disappointed.

David