8139838: Bug in PrismFontFactory generates NullPointerException when loading .ttc font

[Phil Race]

Bug: https://bugs.openjdk.java.net/browse/JDK-8139838
webrev : http://cr.openjdk.java.net/~prr/8139838/

Adds loadFonts() equivalents of the existing loadFont().
The existing loadFont() will now not NPE and will just return the first 
font in the collection.
I have tested this on Mac, Linux and Windows using the included manual 
LoadFonts.java test
and supplying fonts that are not platform fonts. I also verified the 
temp files are cleaned up.

-phil.