capture.cpp: saveImage.sh changes
capture.cpp: saveImage.sh changes

Call saveImage.sh instead of saveImageDay.sh or saveImageNight.sh.
Changed the way arguments are passed.
Rename saved file to final name (e.g., image-20211225010203.jgp) so the name is unique.
Made some variables needed by the save image function global.
Added global "current_bpp" variable and removed bytesPerPixel() function.  Changed all "bpp" to "current_bpp".
Added "-save_dir" command-line argument to specify the directory in which to save the image.
Added error check for non-existent image file name extension.

These changes are not related to saveImage.sh changes:
Made some global variables local to getRetCode()
Added comments for future enhancement to cvText()
thomasjacquin/allsky,thomasjacquin/allsky,thomasjacquin/allsky