added option for titleless window

[fmuecke]

I wanted a more compact view for the hourglass window - so I removed the title bar.

• The title bar can now be toggled off or on via the Advanced options → Windows title → None
• The title-less window can be moved and resized via mouse (is draggable).

[dziemborowicz]

Thanks for this!

Merged this manually as c874899b90751a9459a5661275894073255aacd7 with minor changes:

• Updated Usage.txt to mention the new command-line option.
• Set MainWindow.Title even when WindowTitleMode is None because this string is needed for the taskbar, Alt+Tab, etc.
• Moved logic to set WindowStyle to an UpdateWindowStyle method that is called from a few places. This makes sure that everything to do with what "kind" (for lack of a better word) window we are showing is set in one place and always the same way.

The top border that doesn't go away is annoying. There is no fix for that, it seems, that would work well with the existing code in .NET Framework 4.0, so I did a couple of follow up commits:

• Update to .NET Framework 4.5 (7ff54f9e3aff759f7bc3e71159c7d2af34c1e6de)
• Used the new WindowChrome property to hide the title bar instead of setting WindowStyle to None, which preserves the ability to resize while getting rid of the title and the top border (1361c7f13293bed65e6b1113ce80804ce7b819ce)