Working on new requirement: Export selected reports in PDF format
together with metrics values and TIC graph.

Using itextpdf (www.itextpdf.com) for exporting reports in PDF format. 
Downloaded and added itextpdf-5.4.3.jar in lib directory. 
pom.xml: Added a new dependency itextpdf (version 5.4.3).
Created new class ReportPDFExporter.java to build and save PDF file from
the report unit (In progress - added list of TODOs).
ViewerFrame.java: Added menu item "Export Selected Reports as PDF" and
corresponding action handler. 
DataEntryForm.java: Added new method displayPDFDirectoryChooser() to
select location for saving PDF report file.
Constants.java: Added useful constants.