adorn the mac dock icon with the name of the current project

still need to work with paul on a good treatment for the display of the project name
more work on dock tile adornment
Merge pull request #80 from rstudio/feature/mac-project-badge

adorn the mac dock icon with the name of the current project
OS X 10.7 compatiable CGColorRef conversion
use blue background color for project-name in dock tile
only show dock tile label when there is more than one instance of rstudio running