Split massive CModHandler class/file into multiple parts:

- IdentifierStorage is now a separate handler in VLC
- Renamed ModHandler::Incompatibility exception to ModIncompatibility
- Extracted ModScope namespace from ModHandler
- Extracted ModUtilities namespace from ModHandler
- Split CModHandler.cpp on per-class basis
- Replaced some direct members with unique_ptr to reduce header includes

lib/modding/ModIncompatibility.h

@@ -0,0 +1,42 @@
+/*
+ * ModIncompatibility.h, part of VCMI engine
+ *
+ * Authors: listed in file AUTHORS in main folder
+ *
+ * License: GNU General Public License v2.0 or later
+ * Full text of license available in license.txt file, in main folder
+ *
+ */
+#pragma once
+
+VCMI_LIB_NAMESPACE_BEGIN
+
+class DLL_LINKAGE ModIncompatibility: public std::exception
+{
+public:
+	using StringPair = std::pair<const std::string, const std::string>;
+	using ModList = std::list<StringPair>;
+
+	ModIncompatibility(ModList && _missingMods):
+		missingMods(std::move(_missingMods))
+	{
+		std::ostringstream _ss;
+		for(const auto & m : missingMods)
+			_ss << m.first << ' ' << m.second << std::endl;
+		message = _ss.str();
+	}
+
+	const char * what() const noexcept override
+	{
+		return message.c_str();
+	}
+
+private:
+	//list of mods required to load the game
+	// first: mod name
+	// second: mod version
+	const ModList missingMods;
+	std::string message;
+};
+
+VCMI_LIB_NAMESPACE_END