Popular tags

[florian]

Add popular tag listing to the API, requires a new task and result type.

Input:

• Languages to fetch popular tags for.
• Number of tags to fetch (<= 30).

Output:

• Tag names and relative popularity of the tag as float in [0,1]. If the material count of the popular tags range from 20 to 100 the tag with 100 materials would get a relative popularity of 1, the one with 20 a relative popularity of 0.