Fix wrong text size for some fonts with spaces in their name

In protocol message for TextSizeMeasurement we are rendering font name
(family) as array. This array was used directly in
FontSizeCalculation.js#_measureItem to set the measure element
fontFamily CSS property. A valid CSS fontFamily string is needed instead
(font names with spaces need to be surrounded with quotes).

Use rwt.html.Font class to construct valid CSS font properties.

446182: Label sizes calculated wrong for some fonts on Chrome
https://bugs.eclipse.org/bugs/show_bug.cgi?id=446182

Change-Id: Ib9f667d5f44bf8c83337f46c69ad20899e9a2095
Signed-off-by: Ivan Furnadjiev <ivan@eclipsesource.com>