removal of Control#uia_element dependency

## Description
This is the first pass at removing the MsUia::Control's dependence on a native window handle.  Everything that was using Control#uia_element before is no longer doing so, and instead of hanging on to the `IUIAutomationElement *` (the `uia_element`) now the controls will send the `@locators` information into the `UiaDll` and let *it* decide how to find it.

The next step will be to _completely_ remove the dependence on `HWND` values, allowing us to be able to work with anything that the accessibility framework sees (i.e. WPF apps, etc.).

## Caveat
A couple of the specs run slower than they did before now (I believe the ones for `ListBox` and `SelectList` in particular).  I plan on correcting this, as this is just the first phase.