Always open menubar app on clicked screen

[fabien-d]

What does this PR do?

• Open the menubar app on the screen that was clicked, not always the focused one.
• Separate the workaround so it can easily be removed if/when electron fixes in core.

How should this be manually tested?

Open the menubar example app on separate displays with various configuration (vertically stacked, horizontally stacked) and make sure it always aligns properly

What are the relevant issues?

• Menu always opens on active display on OSX #19
• Work around Electron display focus issues #20
• OSX tray icon clicks always report icon 'bounds' on focused screen electron/electron#1847
• Problem with the window, could not show on Windows 8.1 #32

[fabien-d]

Updated with a Windows fix for #32. Appears if when the bounds get set, the y value doesn't take the app height into consideration.

[tommoor]

Would be useful for muan/mojibar#3 - any problems with this one @maxogden ?

[max-mapper]

Sorry missed this one. LGTM

[fabien-d]

We've been using this code in a production app for a few weeks and no bugs have been reported since.

[eazydripz]

Thank you.