Core/Config: User-friendlyfy configuration parsing errors

It will now print useful error messages that pinpoint the issue
with the config file (missing file, bad syntax, etc)

In memory of MitchesD that lost 18 hours finding a problem with
his config because of a duplicated line.

src/server/shared/Configuration/Config.cpp

@@ -25,7 +25,7 @@
 
 using namespace boost::property_tree;
 
-bool ConfigMgr::LoadInitial(std::string const& file)
+bool ConfigMgr::LoadInitial(std::string const& file, std::string& error)
 {
     std::lock_guard<std::mutex> lock(_configLock);
 
@@ -34,25 +34,32 @@ bool ConfigMgr::LoadInitial(std::string const& file)
     try
     {
         ptree fullTree;
-        boost::property_tree::ini_parser::read_ini(file, fullTree);
+        ini_parser::read_ini(file, fullTree);
 
         if (fullTree.empty())
+        {
+            error = "empty file (" + file + ")";
             return false;
+        }
 
         // Since we're using only one section per config file, we skip the section and have direct property access
         _config = fullTree.begin()->second;
     }
-    catch (std::exception const&  /*ex*/)
+    catch (ini_parser::ini_parser_error const& e)
     {
+        if (e.line() == 0)
+            error = e.message() + " (" + e.filename() + ")";
+        else
+            error = e.message() + " (" + e.filename() + ":" + std::to_string(e.line()) + ")";
         return false;
     }
 
     return true;
 }
 
-bool ConfigMgr::Reload()
+bool ConfigMgr::Reload(std::string& error)
 {
-    return LoadInitial(_filename.c_str());
+    return LoadInitial(_filename.c_str(), error);
 }
 
 std::string ConfigMgr::GetStringDefault(std::string const& name, const std::string& def)