move protocol-reference javascript to a separate file
protocol-reference: only display one code snippet per control (fixes #5)

For each control, one "default" code snippet is determined which makes
the most sense (e.g. a DcsBios::Switch2 for a push button).

Only this "default" snippet is displayed.
Later, we can add an option to display all snippets for advanced users.
Merge pull request #8 from jboecker/fix5

Reference Docs: Show only the most appropriate code snippet for each control