optimize multiline entry

Hi,
your frame implementation is not very nice, since you draw the frame yourself. You should use a native frame to keep the native feeling and honor users theme settings.
Placing a TextEntry and a PasswordEntry side-by-side shows that the PasswordEntry, still with the Gtk.Entry as backend, is a little taller than the TextEntry.

I sugest add 6 pixels to the lineHeight and set the PixelsAboveLines to 3 pixels... This way they will look alike...  at least they did here on my pc (Xubuntu 14.04)