Add ability to get font information.
Add ability to set custom user agent string.
Merge branch 'fonts' of https://github.com/jeff-h/macgap into master-with-jeffs
Merge branch 'user-agent' of https://github.com/jeff-h/macgap into master-with-jeffs
Add defaultLineHeightForFont
Add ability to run shell commands. No async as yet.
Add shell references
Add callbacks capability (taken from hildjj/macgap).
Merge branch 'callbacks' of https://github.com/jeff-h/macgap into master-with-jeffs

Conflicts:
	MacGap.xcodeproj/project.pbxproj
Merge branch 'fonts' of https://github.com/jeff-h/macgap into master-with-jeffs
Merge branch 'shell' of https://github.com/jeff-h/macgap into master-with-jeffs

Conflicts:
	MacGap.xcodeproj/project.pbxproj