replace all '_' with spaces in event names

This incnsitency was confusing, i choose to use spaces becasue thats
what most event names used.

src/actions/attack.cpp

@@ -1487,13 +1487,13 @@ void advance_unit_at(const advance_unit_params& params)
 
 		if(params.fire_events_)
 		{
-			LOG_NG << "Firing pre_advance event at " << params.loc_ <<".\n";
-			resources::game_events->pump().fire("pre_advance", params.loc_);
+			LOG_NG << "Firing pre advance event at " << params.loc_ <<".\n";
+			resources::game_events->pump().fire("pre advance", params.loc_);
 			//TODO: maybe use id instead of location here ?.
 			u = resources::units->find(params.loc_);
 			if(!unit_helper::will_certainly_advance(u))
 			{
-				LOG_NG << "pre_advance event aborted advancing.\n";
+				LOG_NG << "pre advance event aborted advancing.\n";
 				return;
 			}
 		}
@@ -1619,7 +1619,7 @@ void advance_unit(map_location loc, const std::string &advance_to,
 	if(fire_event)
 	{
 		LOG_NG << "Firing post_advance event at " << loc << ".\n";
-		resources::game_events->pump().fire("post_advance",loc);
+		resources::game_events->pump().fire("post advance",loc);
 	}
 
 	// "sighted" event(s).

src/actions/move.cpp

@@ -923,8 +923,8 @@ namespace { // Private helpers for move_unit()
 	 */
 	void unit_mover::try_actual_movement(bool show)
 	{
-		static const std::string enter_hex_str("enter_hex");
-		static const std::string exit_hex_str("exit_hex");
+		static const std::string enter_hex_str("enter hex");
+		static const std::string exit_hex_str("exit hex");
 
 
 		bool obstructed_stop = false;

src/game_events/menu_item.cpp

@@ -59,7 +59,7 @@ namespace { // Some helpers for construction.
 	 */
 	inline std::string make_item_name(const std::string & id)
 	{
-		return std::string("menu_item") + (id.empty() ? "" : ' ' + id);
+		return std::string("menu item") + (id.empty() ? "" : ' ' + id);
 	}
 
 	/**

src/playsingle_controller.cpp

@@ -268,7 +268,7 @@ LEVEL_RESULT playsingle_controller::play_scenario(const config& level)
 		pump().fire(is_victory ? "victory" : "defeat");
 		{ // Block for set_scontext_synced_base
 			set_scontext_synced_base sync;
-			pump().fire("scenario_end");
+			pump().fire("scenario end");
 		}
 		if(end_level.proceed_to_next_level) {
 			gamestate().board_.heal_all_survivors();