Adding build-set to working file set

[David Nolden]

So the main question is, whether it really makes sense to tie build/target-
sets to working sets.

Whether it makes sense depends on:
Do people
A) Use working sets to switch between completely different tasks (Different 
files/executables/targets/etc.)
or
B) Do they use working sets to switch between different file-sets while 
working on the same task.

In case A), it makes sense to switch the build-set as well, in case B) not at 
all.

Actually my initial idea for working sets was B), but I've found myself using 
them in the A) way, that's why I got the idea to tie build-set ond working-set 
together.

But we've got to think about how this relates to session support, so working-
sets don't become a replacement for sessions.

Greetings, David