Add a simple admin test script to exercise the macOS bundle

[PaulWessel]

Description of the desired feature

After building the macOS bundle I usually install it, double-click on the logo and get the terminal set up to use the bundle executables. I then run a few basic commands to ensure that GMT works and that the included tools like ghostscript, gm and ffmpeg works. However, this is of course a bit incomplete. The bin directory also contains gdal_translate and ogr2ogr which I usually do not remember to check. Finally, I have at least once been tricked because my environment has defined GMT_SHAREDIR and gmt uses that instead of the bundle default. So I had to unset that one.

It would be nice to have a script that does the following:

1. Unsets any GMT_* environment parameters
2. Applies the one suggested in the GMT bundle splash screen:
   a) export GMTHOME=/Applications/GMT-6.4.0.app/Contents/Resources
   b) prepend $GMTHOME/bin to your path
   c) export PROJ_LIB=$GMTHOME/share/proj
   d) export GS_LIB=$GMTHOME/share/ghostscript/Resource/Init
   e) export MAGICK_CONFIGURE_PATH=$GMTHOME/lib/GraphicsMagick/config
3. Runs a 1-liner coast command that plots coastlines (GSHHS) and paints a specific contry (DCW) and makes PDF (ghostscript)
4. Plots a shapefile (e.g. @RidgeTest.shp) to exercise ogr2ogr
5. Convert a nc file (e.g., @HI_topo_02.nc) to something else (gdal_translate)
6. Runs the simple spinning globe movie and makes a GIF (gm) and a MP4 (FFmpeg)

The script could be added to the admin folder (e.g., test-bundle.sh)