Grid: allow tabs/spaces in area strings

[schuetzenhofer]

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This assertion would trigger if there are tabs in the area strings.

jassert (s.size() == strings[0].size()); // all rows must have the same number of columns

For readability formatting the strings to resemble the grid would make sense. Example_

grid.templateAreas = { 
"empty   empty   empty   empty   empty   empty   empty",
"undo    redo    blank   btnA    btnB    btnC    settings",
"empty   empty   empty   empty   empty   empty   empty" 
};