bot: implemented asynchronous pathfinding

nav: floyd-warshall matrices and practice updates are done asynchronously by now
add: yb_threadpool_workers cvar, that controls number of worker threads bot will use
add: cv_autovacate_keep_slots, the amount of slots to keep by auto vacate
aim: enemy prediction is now done asynchronously by now
bot: minor fixes and refactoring, including analyze suspend mistake (ref #441)

note: the master builds are now NOT production ready, please test before installing on real servers!

ext/hlsdk/extdll.h

@@ -39,11 +39,9 @@ private:
    estring_t offset;
 
 public:
-   explicit string_t () : offset (0)
-   { }
+   explicit string_t () : offset (0) {}
 
-   string_t (int offset) : offset (offset)
-   { }
+   string_t (int offset) : offset (offset) {}
 
    ~string_t () = default;