declarative plasmoids and services

[Alex Merry]

While developing the nowplaying QML plasmoid (see previous email), I ran
into problems using services where
service.startOperationCall(service.operationDescription("Play"))
would fail ("Play" takes no arguments), because startOperationCall would
get an invalid KConfigGroup (with no name).

It turned out that this was because I was storing the service in a
QtObject property, and some sort of typing information about functions
was being lost.  The solution was to always call serviceForSource() at
the point where I needed to use the service.

However, the design pattern for services is to always create a new one,
so we've either got a memory leak (if they don't go away), or
setAssociatedWidget() isn't going to work (if they do).

Brief testing suggests that setAssociated[Widget/Item]() works (subject
to https://git.reviewboard.kde.org/r/104760/).  That may indicate the
leak scenario, or I may have just been (un)lucky with garbage collection.

Is this something that needs to be dealt with?  Perhaps in libplasma2?

Alex