Add Ability to Select Plot Line

1) Added delegate functions for handling down and up events while over the plot line.
2) Added delegate functions for handling the selection and deselection of the plot line.
3) Added delegate function for performing graphics operations just before drawing the plot line.
Fixed some static analyzer warnings.
Clear the isDragging flag on a pointing device up event. Coding style updates. Fixed issue #65.
Added Mike Rossetti to the license.
Changed the plot data line hit detection path to use Core Graphics for cross-platform support.
Renamed the scatter plot line selection delegate methods to standardize the naming scheme. Coding style updates. Fixed issue #23.
Added scatter plot data line selection demos to the Plot Gallery app.
Removed the data line was deselected delegate methods.
Fixed a memory leak.
Documentation updates.
Merge branch 'mrossetti-release-2.0'