feat(bkgpslog):Consolidate write ops into one function

feat(bkgpslog):Consolidate write ops into one function

Create metafunction 'magicWriteBuffer' to be triggered for
asynchronous appending of location files into tar file via
appendArgTar function (new) once buffer filled in main logging loop.

Create appendArgTar function to append a bash variable as a file to a
tar file.