Code optimization and bug fixes
- Removed redundant code
- Fixed two small bugs in the distance_client calculation
- Improved the "step action" system added in the last commit
  * Added a "unit_step_timer" that is now used for all step actions; now even skills will always be executed at "full cell" (if you don't lag)
  * The "step action" system will no longer mess with anything and rather just call the normal attack/skill functions that are also called by the client; this removes a lot of unneeded code and also works a lot better since the existing functions have been bug-tested the most; this also fixes a problem with the "auto-follow if you can't reach target" system