Remove compound terms (strenger) from drop down menu

[kyrretl]

They clutter up the drop down list and are available in the infobox anyway

[danmichaelo]

Fixed in 67e71e7

[danmichaelo]

We should probably test this and get opinions from more people. In 67e71e7 I tried removing all compound headings.

However, I wonder if we should keep the true compound headings (Topic : Topic), and just leave the virtual ones (Topic : Place/Time/GenreForm) out.

We only have about 1k true compound headings, but more than 10k virtual ones, so leaving out the virtual ones should still help a lot.