Fix failing FF layout tests

Some of the new layout tests fail in Firefox: http://127.0.0.1:8124/webodf/tests/tests.html?suite=LayoutTests

* Modified chosen font pt size to avoid FF vs Chrome font size rounding differences
* Allow multiple accepted values in LayoutTests to cope with the fact that FF converts the vertical align property into px, whilst Chrome leaves it as a percentage.
Drive-by changes make your :hand:s fall off and your :nose: grow oversize, did nobody tell you when you were young?
Please a separate commit with proper message. Helps to keep your body unchanged and also a future git-blame-reader. Win-win.