install.sh attempts to replace PRISM_DIR=... with the actual PRISM directory
in the startup scripts contained in bin/ using a call to sed.
On MacOS, the system sed fails with 'RE error: illegal byte sequence' for binary
files, such as the .DS_Store files created by the Finder.
So, we exclude all files starting with a dot (.*) as well. Additionally,
we use `-iname` instead of `-name` in the find command for the matches
against '*.bat' and 'ngprism' to match insensitive to the case of the filename.
[adapted by @kleinj from PR #59]
Steffen Märcker