Fixed segfault, minion targeting, added attack move

- Fixed a case where a segfault could occur when a unit target was still
set on dead units. There's still another case of a segfault in this
patch at Minion::update which I can't identify. Would be great if
someone could track this down.
- Fixed indentation in Unit::update
- Fixed autoattacks being cancelled when trying to last hit
- Updated Minion targeting, it should prioritize targets now
- Added attack move and added isDead check
- Added std namespace to min/max functions to prevent ambiguity
- Added some comments to announcer events