Add settings API and specification

The details of the API are in the `/docs/specsSettings-API.md` file.

The enums do not list all available settings, more are to be added as
the settings API replaces inline QSettings calls.

build_scripts/qt/sources.pri

@@ -15,10 +15,11 @@ SOURCES += src/main.cpp\
     src/openvr/ivrinput.cpp \
     src/utils/setup.cpp \
     src/utils/paths.cpp \
-	src/utils/FrameRateUtils.cpp \
+    src/utils/FrameRateUtils.cpp \
     src/openvr/overlay_utils.cpp \
     src/keyboard_input/keyboard_input.cpp \
-    src/keyboard_input/input_parser.cpp
+    src/keyboard_input/input_parser.cpp \
+    src/settings/settings.cpp
 
 HEADERS += src/overlaycontroller.h \
     src/tabcontrollers/AudioTabController.h \
@@ -46,10 +47,15 @@ HEADERS += src/overlaycontroller.h \
     src/openvr/ivrinput.h \
     src/utils/setup.h \
     src/utils/paths.h \
-	src/utils/FrameRateUtils.h \
+    src/utils/FrameRateUtils.h \
     src/openvr/overlay_utils.h \
     src/keyboard_input/input_parser.h \
-    src/keyboard_input/input_sender.h
+    src/keyboard_input/input_sender.h \
+    src/settings/settings.h \
+    src/settings/setting_value.h \
+    src/settings/settings_internal.h \
+    src/settings/settings_controller.h \
+    src/settings/specific_setting_value.h
 
 win32 {
     SOURCES += src/tabcontrollers/audiomanager/AudioManagerWindows.cpp \