Fixed incorrect merge from other branch
Replaced usage of UIItem.Pattern(...) with extension method GetPattern<TPattern>()
Fixed issues with WPF ComboBox.

Made ComboBox collapse itself after selection if item requested to select is already active and thus Select just returns.

Absence of this code leads to problems in case when client code tries to select already selected item. Then base.Select(itemText) or base.Select(index) do nothing and combo box stays open. Next user actions may not expect this which could lead to confusing results. For example, after selection in combo box client code wants to click on check box below - White emulates click on the place where check box is located, but combo box drop down is at the place, so some another item is selected. So, we have to close combo box regardless of the fact that selection did something.

For same reasons added ComboBox collapsing after getting SelectedItem and SelectedItemText.
Without this change ComboBox expansion lags behind SelectionItemPattern.Select() which throws InvalidOperationException for some reason.
Fixes possible COMException during Window.WaitForProcess() execution.

If process exited already, then automationElement.Current.ProcessId throws COMException with E_FAIL. Hence, instead of getting processId every time, we'll take everything we need at ctor time and just use it afterwards.
Fixes #186: TextBox.Text property assignment types only part of text.
The problem with InvalidOperationException was related to the fact that IsSelected was false when checked, but already becomes true until control flow reaches pattern execution. Hence instead of falling back to patterns immediately, we'll wait a bit to give mouse click a chance to be handled.
Made waiting for input idle tolerate already closed window situation
Cleaner solution for #186
Cleanup: used GetPattern<T>() in rest of places
Added ComboBoxItemSelectionTimeout to settings so that this value could be customized
Added some precaution for ListItem.Select() in case of sluggish UIs.
Merge pull request #199 from ivan-danilov/some-uia-v3-fixes

Some uia v3 fixes