File chooser and drag and drop capabilities for property components

Here's a suggested change for the Introjucer. It adds file chooser and drag and drop where TextPropertyComponents are currently used to select folders. Non-breaking and practically drop-in... :) 


(fighting the forum slightly today - it really want to double space the code!)

Example of use: 

            for (Project::ExporterIterator exporter (project);;)

                props.add (new FilePropertyComponent (exporter->getPathForModuleValue (moduleID),

                                                      "Path for " + exporter->getName().quoted(), true, "*", project.getProjectFolder()),

                           "A path to the folder that contains the " + moduleID + " module when compiling the "

                            + exporter->getName().quoted() + " target. "

                           "This can be an absolute path, or relative to the jucer project folder, but it "

                           "must be valid on the filesystem of the target machine that will be performing this build.");

And it even sorts out the relative paths automatically :)

Cool - thanks Jim, will have a look!