Observed in SVN r18582

To Replicate:
* Open an existing GNUCash file
  * Note that in the primary window that the Accounts tab is "un-deletable"
* Open a secondary window
  * Note that there is no Accounts tab present
* Close the primary window
* Note that there is no menu item to add an accounts tab at least in
  * Window menu
  * File > New menu (2.2.9 behavior)


Expected Behavior:

* Would be able to add an Accounts tab to any window using the Window menu



Suggested Resolution Approaches:
(In order of personal preference)

1)
* Add "Show Accounts Tab" menu item to Window menu
* Have that menu item be able to hide the Accounts tab as well (toggle state)

2) 
* Add "Show Accounts Tab" menu item to Window menu that is only in an active state if the Accounts tab is not shown

3) 
* Add "Add Accounts Tab" menu item to Window menu that always adds an Accounts tab to the current window, even if on already exists


Discussion:

I find the "File > New" menu an in-obvious place for revealing the Accounts tab. I can accept that the Budget creation goes there, because I'm conceptually creating something new. However, with the Accounts tab, I'm not creating anything new, I'm just showing something that already exists -- a summary of my chart of accounts. Similarly, adding a report tab doesn't come from "File > New"