Enhancement for selecting new or any opened window - #395

Code changes:
added 'Close Window And Select' to simplify two steps of 'Close Window' + 'Select Window'
added 'List Windows' to return all current handles;
enable 'Select Window' to always return the handle of window it is selecting from, and only return handle if 'self' as locator;
enriched 'Select Window' to select any opened window by a window handle;
enriched 'Select Window' to select new window by excluding a list of earlier window handles;

Background:
It is very useful to surface window handle to users that want to have the 'correct way' - comparing window handle sets, to switch window. If we do this way, the fix here for 'Close Window' is not required. instead, my new proposal is to update 'Select Window' and add 2 keywords:

Close Window And Select | locator=None

This will close current window and then switch to window if locator is given. locator can be name, title, url, handle, ..., the same as 'Select Window' requires.

${previous_window}= | Select Window | locator=None

This will switch to window matching locator and return previous window's handle. locator can be name, title, url, handle of target window, or a handle list to exclude in order to find new window. If locator is 'self', only return current window handle.

${window_list}= | List Windows

This will return a list of all opened window handles in same session not assuming its order.

Above changes should not impact existing usage of 'Close Window' and 'Select Window', and can offer the strict 'correct way' for using handle to switch window.

example 1:
A user should save main window handle in the beginning if required:

Open Browser 
${main_window}= | Select Window | self

A user can switch to correct window like below:

${all_old_windows}= | List Windows
Click Link | xxx | # or any other action that generates a child window
${parent_window}= | Select Window | ${all_old_windows}
Other Actions Against The Child Window
Close Window And Select | ${parent_window}

One more consideration:
should we also offer the additional simplified way to select the last-position indexed window as new window without the need to comparing with old window handles? The doc can prompt user to use strict way to select new window if the simplified way does not work for him/her. From my experiences the simplified way will be correct in 99% cases.

${parent_window}= | Select Window | new