Make mapping argument to autopilot NULL by default

This allows to not specify aes() in the function call and to depend less directly on ggplot2 being loaded.
Fix long lines in comments
Suggest mapproj which is used in ggplot2 related plotting functions
Prefix all ggplot2 functions with ggplot2::

Allows to just import the package and not actually load it.
Add an example on how to use the mapping argument in autoplot.bathy
Fix documentation

Missing arguments
Missing documentation entries
etc.