* citra-qt config: small misc changes
Remove unused ReadSettingGlobal
Remove unused WriteSetting overload
ReadGlobalSetting: rename default value variable
* qt config: fix u16 values being written as QMetaType
* qt config: rework post processing shader setting
handles post processing setting properly when per-game settings are used.
the anaglyph shader is given its own setting, separate from the post
processing name.
* qt config: use u32 instead of unsigned int when casting