Let ROS log to tmpfs

[mklomp]

ROS is logging a lot which:

1. Does writes to the SD card which is not helping in wear and tear.
2. It might at some point create an empty space error.

With logging to tmpfs you will of course loose the logs of previous boots, but that seems fine.

[ArendJan]

We also need to give tmpfs mount a max size and make sure that ROS works nicely with that limit