Build-plugin: Rework build target selection/execution
- Remove "default target", execute first command in target-set in stead
- Remove the check-box for "default target"
- Add sorting buttons to move commands/target-sets up or down
- Move "default targets" from old configs to be first in the target-set
- Fix flags for run column: select-able and same background as the rest
- Fix copyright header
@neundorf You might have opinions and input on this too