Add license headers to shell and python scripts

[ggreptile]

• Commit 1: Modify contrib/add_missing_license_headers.sh to also mark Python and Shell scripts
• Commit 2: Execute and add license headers to existing scripts

[parazyd]

Hey, thanks for the effort!

A couple of issues:

• A lot of the scripts have changed their file permission (got the executable bit removed)
• The license header provided in contrib is a C-style comment, so it is not applicable to shell scripts or python. They need to begin with #

While you're at it, perhaps it would be useful to add lists in the script where we could set files we want to exclude from changing.
Also, some files have other people's copyright as well. We could actually make the script a bit smarter, where we could optionally add a specific string below the Dyne.org copyright, referencing the other copyright. Nothing exotic, just an arbitrary string that would appear on the line below our copyright. Then to add the license headers we can do them in another PR or I can add them myself by running the script :)