Default music dir and refactoring of collection config

[Jeff Mitchell]

Maximilian Kossick wrote:
> Congratulations, now you know one person on Linux who puts the music
> in ~/Music :)
>   
You weird wacko you  :-)

> Are you referring to those XDG environment variable that we had
> trouble with a few months ago?
>   
Yep.

> I don't think this has anything to do with this.
It does...from the blog post it seems like on Linux it uses xdg under 
the hood, but that doesn't really matter at our level.

> And it's supported by
> Qt anyway. It's probably the job of the linux distro to provide a way
> to change the default dir,
> not of Qt. And the spec itself allows for that.
>   
Yes, but my point was...how many lay users are going to figure that 
out?  Think especially of Mac and Windows users, now...will normal users 
know which plist to change?  Which registry key?  If Qt can support that 
it'd be really nice.

> but the local collection is still going to be the first among equals,
> so a special treatment of its configuration could make sense.
>   
There's that singular "collection" again...have we ditched the idea of 
support of multiple local collections?

--Jeff