Provide accessible Checkable list (PR #7491)
Implements an accPropServer for NVDA to be able to use checkableLists. accPropServer is a base class users can inherit from to implement accpropServers on wx widgets.
This commit introduces
- an accessible check list box, so that each item is a checkbox. This list box only supports one column
- CheckableAutoWidthColumnListCtrl, which is a multi column supporting list control with accessible check boxes. From an accessibility perspective, this control behaves similar to the list control in Windows disk cleanup (cleanmgr).
- an abstract AccPropServer we can make other servers from. This helps with fixing accessibility, but wraps the callback you provide with exception handling code (Since comtypes seems to squelch errors).
closes #7325
closes #4357
