Add Group::DEFAULT_NAME

So that the constant is accessible to LOOT at compile time.

include/loot/metadata/group.h

@@ -35,6 +35,11 @@ namespace loot {
  */
 class Group {
 public:
+  /**
+   * The name of the group to which all plugins belong by default.
+   */
+  static constexpr const char* DEFAULT_NAME = "default";
+
   /**
    * Construct a Group with the name "default" and an empty set of groups to
    * load after.

src/api/metadata/group.cpp

@@ -27,7 +27,7 @@
 #include "api/metadata/yaml/group.h"
 
 namespace loot {
-Group::Group() : name_("default") {}
+Group::Group() : name_(Group::DEFAULT_NAME) {}
 
 Group::Group(const std::string& name,
              const std::vector<std::string>& afterGroups,