hector_slam tutorials: -Add arguments to launch files for specifying geotiff file path

Saving geotiff files to the default folder (the "maps" subfolder of the hector_geotiff package) is not possible when hector_slam is installed from .debs so far. This pull request adds arguments to launch files so the geotiff save path can be set from the tutorial launch command line like so:

<pre>
roslaunch hector_slam_launch tutorial.launch geotiff_map_file_path:=$HOME
</pre>

Will update http://wiki.ros.org/hector_slam/Tutorials/MappingUsingLoggedData after this has been pushed through to .debs.