Better support running from a local catkin workspace

[peci1]

Currently, running a multirobot simulation (or multiple simulations) directly from local catkin workspace has its quirks. This PR addresses them.

1. robot_data bag files need to have a different name for different robots (and simulation partitions)... otherwise, all robots try to record to ~/.ros/robot_data_0.bag, and only one of them obviously succeeds.
2. ignition log files (currently hardcoded to /tmp/ign/logs) need a configurable location, so that multiple simultaneous simulations do not write into the same folder.
3. The "simulator rosbag" needs to respect the path set in point 2. (currently, it hard-codes /tmp/ign/logs regardless of the <path> setting of GameLogicPlugin)

I think I saw some initiative towards 2. somewhere (passing a CLI arg with the path instead of having it hardcoded in the launch file), but I can't remember where it was.

Also, the parametrization of ign launch files with the log path would need to modify all of the provided files. I modified just cloudsim_sim.ign, and when we agree whether it's a good approach, I'd modify all of them.

The renaming of robot rosbags might break backwards compatibility for Docker users - the names of the files would change. I'm not sure if this is acceptable or not, but I can imagine some workarounds that would keep the original name if Docker environment is detected (e.g. matching $USERNAME == developer, or checking for nonempty IGN_PARTITION). Local catkin workspace users would also be affected, but as they were using broken logic anyways, it shouldn't actually hurt them.

[osrf-jenkins]

Build finished. 15 tests run, 0 skipped, 0 failed.

[peci1]

This will need to be mentioned in the new release announcement. I suggest the following:

• cloudsim_sim.ign got a new parameter logPath which specifies where to record the simulator logs. Previously, it was hardcoded to /tmp/ign/logs.
• BAG files with robot data are named differently for each robot (and for each IGN_PARTITION). This allows running multirobot simulations from a local catkin workspace. For a robot with name ROBOT, the new name of the rosbags is as follows:
  • if IGN_PARTITION is unset or empty, the files will be named robot_data_${ROBOT}_${i}.bag (previously it was robot_data_${i}.bag).
  • If IGN_PARTITION is non-empty, the files will be named robot_data_${IGN_PARTITION}_${ROBOT}_${i}.bag (previously it was robot_data_${i}.bag).