Make all external links in site truly external

[rlc4]

References to securitybsides.org in the about menu load in the same window as the bsidessf site.
Look for other occurrences of similar behavior and fix all of them to open in a new tab/window.

[rlc4]

Also there are a pile of areas where we are mixing href, external, and url in data files.
We should stick to a standard of what we're using and be consistent throughout our data files.

Proposal:
href - internal links to all anchors (including # anchors)
external - external urls