add [unit_type_fix] in [scenario], [era] etc

fixes #1451

Currently advancements can be changed in two ways:
1) Via [advancefrom], this causes OOS in multiplayer
2) Via certain campaign etra defines, this has other disadvantages see

The new [unit_type_fix] that is accepted in [scenario], [multiplayer],
[era], [modification] , [campaign] and [ressource] changes the advancement
of a unit type only for one game and has non of the disadvantages of
the other two methods.

We should also deprecate the other two methods.

src/play_controller.cpp

@@ -97,6 +97,7 @@ static void copy_persistent(const config& src, config& dst)
 
 	static const std::set<std::string> tags {
 			"terrain_graphics",
+			"unit_type_fix",
 			"lua"};
 
 	for (const std::string& attr : attrs)
@@ -167,6 +168,9 @@ play_controller::play_controller(const config& level, saved_game& state_of_game,
 {
 	copy_persistent(level, level_);
 
+	for(const config& unit_type_fix : level_.child_range("unit_type_fix")) {
+		unit_types.apply_scenario_fix(unit_type_fix);
+	}
 	resources::controller = this;
 	resources::persist = &persist_;
 	resources::recorder = replay_.get();
@@ -188,6 +192,7 @@ play_controller::play_controller(const config& level, saved_game& state_of_game,
 
 play_controller::~play_controller()
 {
+	unit_types.remove_scenario_fixes();
 	hotkey::delete_all_wml_hotkeys();
 	clear_resources();
 }

src/saved_game.cpp

@@ -331,6 +331,11 @@ void saved_game::load_mod(const std::string& type, const std::string& id, size_t
 		for(const config& modlua : cfg.child_range("lua")) {
 			this->starting_point_.add_child_at_total("lua", modlua, pos++);
 		}
+		
+		// Copy unit_type_fix
+		for(const config& modlua : cfg.child_range("unit_type_fix")) {
+			this->starting_point_.add_child_at_total("unit_type_fix", modlua, pos++);
+		}
 
 		// Copy load_resource
 		for(const config& load_resource : cfg.child_range("load_resource")) {

src/units/types.cpp

@@ -33,6 +33,7 @@
 #include "gui/dialogs/loading_screen.hpp"
 
 #include <boost/regex.hpp>
+#include <boost/range/algorithm_ext/erase.hpp>
 
 #include <locale>
 
@@ -1423,6 +1424,59 @@ const unit_race* unit_type_data::find_race(const std::string& key) const
 	return i != races_.end() ? &i->second : nullptr;
 }
 
+void unit_type::apply_scenario_fix(const config& cfg)
+{
+	if(auto p_setxp = cfg.get("set_experience")) {
+		experience_needed_ = p_setxp->to_int();
+	}
+	if(auto attr = cfg.get("set_advances_to")) {
+		advances_to_ = utils::split(attr->str());
+	}
+	if(auto attr = cfg.get("set_cost")) {
+		cost_ = attr->to_int(1);
+	}
+	if(auto attr = cfg.get("add_advancement")) {
+		for(const auto& str : utils::split(attr->str())) {
+			advances_to_.push_back(str);			
+		}
+	}
+	if(auto attr = cfg.get("remove_advancement")) {
+		for(const auto& str : utils::split(attr->str())) {
+			boost::remove_erase(advances_to_, str);
+		}
+	}
+}
+
+void unit_type_data::apply_scenario_fix(const config& cfg)
+{
+	unit_type_map::iterator itor = types_.find(cfg["type"].str());
+	// This might happen if units of another era are requested (for example for savegames)
+	if(itor != types_.end()) {
+		itor->second.apply_scenario_fix(cfg);
+	}
+	else {
+		// should we give an error message?
+	}
+}
+
+void unit_type::remove_scenario_fixes()
+{
+	advances_to_.clear();
+	const std::string& advances_to_val = cfg_["advances_to"];
+	if(advances_to_val != "null" && !advances_to_val.empty()) {
+		advances_to_ = utils::split(advances_to_val);
+	}
+	experience_needed_ = cfg_["experience"].to_int(500);
+	cost_ = cfg_["cost"].to_int(1);
+}
+
+void unit_type_data::remove_scenario_fixes()
+{
+	for(auto& pair : types_) {
+		pair.second.remove_scenario_fixes();
+	}
+}
+
 void unit_type::check_id(std::string& id)
 {
 	assert(!id.empty());

src/units/types.hpp

@@ -275,6 +275,8 @@ public:
 	/// Attention: Filters in resistance-abilities will be ignored.
 	int resistance_against(const std::string& damage_name, bool attacker) const;
 
+	void apply_scenario_fix(const config& cfg);
+	void remove_scenario_fixes();
 private:
 	/// Generates (and returns) a trimmed config suitable for use with units.
 	const config & build_unit_cfg() const;
@@ -375,6 +377,8 @@ public:
 	/** Checks if the [hide_help] tag contains these IDs. */
 	bool hide_help(const std::string &type_id, const std::string &race_id) const;
 
+	void apply_scenario_fix(const config& cfg);
+	void remove_scenario_fixes();
 private:
 	/** Parses the [hide_help] tag. */
 	void read_hide_help(const config &cfg);