White space fixes

Kerning pair class

Speed optimizations of TTF export code
Exporting kerning pairs is now more than a thousand times faster for big
fonts.

Adjust kerning tab to font height

Efficient parsing of the kern table

menu items for removing kerning classes

Remove PairPosFormat2

Kerning by classes
This implementation uses the PairPosFormat1 to store kerning values in
TTF files and has a new kerning display that allows the user to define
kerning classes.

Some code to do PairPosFormat2 is included as well but it seems like
the PairPosFormat1 is the better solution.

Merge branch 'master' of gitorious.org:birdfont/birdfont

4096 units per em

Merge branch 'master' of gitorious.org:birdfont/birdfont

mac issues, including a more permissive license for libbirdfont

Subdirectory for open font format tools