[settings] Add settings component

This adds a new settings component for user configurable options that
can be changed through the JSON API.
The settings are stored in the admin db table and not in the conf-file.

src/settings.h

@@ -0,0 +1,65 @@
+
+#ifndef __SETTINGS_H__
+#define __SETTINGS_H__
+
+#include <stdbool.h>
+
+
+enum settings_type {
+  SETTINGS_TYPE_INT,
+  SETTINGS_TYPE_BOOL,
+  SETTINGS_TYPE_STR,
+  SETTINGS_TYPE_CATEGORY,
+};
+
+struct settings_option {
+  const char *name;
+  enum settings_type type;
+};
+
+struct settings_category {
+  const char *name;
+  struct settings_option *options;
+  int count_options;
+};
+
+
+int
+settings_categories_count();
+
+struct settings_category *
+settings_category_get_byindex(int index);
+
+struct settings_category *
+settings_category_get(const char *name);
+
+int
+settings_option_count(struct settings_category *category);
+
+struct settings_option *
+settings_option_get_byindex(struct settings_category *category, int index);
+
+struct settings_option *
+settings_option_get(struct settings_category *category, const char *name);
+
+int
+settings_option_getint(struct settings_option *option);
+
+
+bool
+settings_option_getbool(struct settings_option *option);
+
+char *
+settings_option_getstr(struct settings_option *option);
+
+int
+settings_option_setint(struct settings_option *option, int value);
+
+int
+settings_option_setbool(struct settings_option *option, bool value);
+
+int
+settings_option_setstr(struct settings_option *option, const char *value);
+
+
+#endif /* __SETTINGS_H__ */