Adding build-set to working file set

[David Nolden]

I think the build-set still lacks flexibility and manageability.

Now the targets you want to build usually correlate with the files you edit, 
so what about merging the build-set into the working-set?

To make it even more consistent, I propose renaming "Buildset" to "Targetset". 
Then the working-set tooltip would show under the "Documents:" a "Targets:" 
list if t here is a target-set, allowing easy management and overview of build 
targets.

Also, that target-set could/should be used as default 'run' or 'debug' target, 
if there is only one runnable target in the target set, else a selection 
dialog could be shown.

Last but not least, if it is empty the target-set should be auto-filled with 
the target that contains the currently active file, or if there is no active 
file, with all currently open projects.

Using that scheme, we could solve some usability problems, as the simple cases 
would work configuration-less:
- Usually, if you have one executable in your build-set, you will also want to 
run/debug that one
- Usually, if you edit a source file that belongs to one executable, you will 
also want to build/run/debug that executable

And for the more complex cases, the working sets would allow comfortable 
management of the build set.

Greetings, David