web: add simple cgi scripts to generate diagnostics and export snapshots

The common way is that users can generate diagnostics as well as export schnapshots in reForis but it is harder to get them once reForis is crashing. This instead is little script that provides the same functionality (although in not that nice coating) and works without reForis. It covers situation when reForis does not work but Lighttpd does and prevents need for users to go to shell to get diagnostics.

Requires bootstrap-theme!3 (merged), schnapps!35 (closed) and bootstrap theme from turris/os/packages!871 (merged).