Split general into multiple threads

[Seb via Digitalmars-d]

I think we all agree that general is having to much traffic and 
according to CyberShadow [1] this again is just an approval 
issue, however I expect this a bit controversial, so please no 
OT! Only other category proposals.

Proposed categories:

- DMD
- DRuntime
- Phobos
- Language design (or Idea pool)
- D Foundation + resources
- Events
- Other (formerly known as General)

I want to stress that whatever categories we pick, we have to 
adapt them anyways if we realize that something is noisy again or 
too silent.

https://github.com/CyberShadow/DFeed/issues/66