I noticed there isn't "Extension manager" in "Tools" menu in my VS2015 community anymore! What may have caused that?
I uninstalled it, then re-install VS2015 professional and found it again right after the first launch. The next launch it disappeared again (with the other extensions as well) !
This is what I've done so far:
1- Uninstall again.
2- Delete "extensions" folder from "C:\user(USERNAME)\local\microsoft\Visual Studio\14.0"
3- Reinstall (pro version).
4- Same problem !
For anyone encountering this issue, after many useless uninstallings: Run (from start menu) "Visual Studio professional" not "Visual Studio Blend"... that's all :)