[mapplauncherd] Reset oom_score_adj instead of oom_adj if needed
[mapplauncherd] Rename invoker --daemon-mode to --keep-oom-score

The old name was vague and didn't indicate the change in behavior at
all. Its documentation also described the behavior incorrectly. If the
-o or --keep-oom-score parameter is passed, the OOM score of the boosted
process will be unchanged. Normally, it will be reset to 0 on launch.

The --daemon-mode parameter is kept as an alias for compatibility.
Merge pull request #16 from special/master

[mapplauncherd] Improve OOM score handling