Language support

[PeterJohnson]

Add info to JSON so that vendor extension browser can filter out based on current project language, since several vendordeps only support one language.

[Starlight220]

Isn't this something that can be inferred from the various artifacts fields?
If something has only Java (and/or JNI) artifacts, it supports only Java; if it doesn't, C++-only; if it has both, support both languages. This algorithm should have very few if at all false detections.

(Python doesn't use vendordeps, right?)