[Geany] change view whitespace character and toogle view whitespace button

[Bob Snyder]

Enrico Tröger wrote:

>> View->Editor->Show line endings
>>     
>
> Done so in SVN.
> There is now a submenu View->Editor->... which holds all five mentioned
> settings. Additionally, I added the Line numbers and Markers margin
> settings to the prefs dialog to keep the settings in sync.
>   

Just built from r3342 and the change works as advertised. Imo, this is a 
substantial improvement. Many thanks Enrico!

Bob S.