add true px value to html font sizes

By using the invalid `apx` value, apps must be built or use the
runtime LESS compiler in order to render correctly. By duplicating
the font-size property with both `px` and `apx`, the former
ensures that debug-mode apps work (because `apx` is ignored as
invalid) and built apps work because the converted `apx` value
overrides the converted `px` value.

Issue: ENYO-595
Enyo-DCO-1.1-Signed-off-by: Ryan Duffy (ryan.duffy@lge.com)