fix fall-back on custom font declaration

Both ways work in the end, but the fall-back happening here is not from one
font family to another but from a possible local installation of the same font
to using a webfont version from the app. The CSS handling this fall-back
should be the font-face declaration, not the family selector.
add webfont resource files for Libertine font family
add config option and styles for Libertine font family
avoid over-riding font family preference if the font has good glyph support
reduce font size boost for Hebrew from 1.5em to 1.2em

The 150% size increase is excessive and makes usage impractical with
several columns open. 1.2 is a more usable default value and works out
so that Hebrew versions take up about the same about of vertical space
as other languages for the same verse range.
fix lib styles
fix