Smelting Gives Experience (#4094)

* Smelting Exp

Smelting now gives experience

* Furnace.txt update

Exp rewards are entered in furnace.txt, Reward calculation is now done
is the furnaceentity class

* furnace.txt update

Changed alignment tabs to spaces
Included documentation of exp in recipe

* Updated StringToFloat

changed strtod to strtof

* Explicit Float to Int

* Reworked Smelting Rewards

* No C casts

-Adds new function to the api
-Sets reward counter to 0 in furnace constructor

* Style and exp lock removed

-Fixed  style mistakes accoring to PR notes
-XP isn't locked to a single player anymore

* No Smelter API

-Removed SetLastSmelter and GetLastSmelter
-Fixed comments
-Fixed log reward amounts

src/StringUtils.cpp

@@ -1051,3 +1051,15 @@ AString StringsConcat(const AStringVector & a_Strings, char a_Separator)
 	}
 	return res;
 }
+
+bool StringToFloat(const AString & a_String, float & a_Num)
+{
+	char *err;
+	a_Num = strtof(a_String.c_str(), &err);
+	if (*err != 0)
+	{
+		return false;
+	}
+	return true;
+}
+