Merge pull request #24 from FreekDB/master

Refactored ReportReader (retrieveReports and checkDataFilesAvailability) and solved some Checkstyle issues
Configured maven-resources-plugin to copy resources to proper location
during the package phase. 
Added class casting in Main.java.
Maven POM is now configured to create executable jar (use mvn
-Dmaven.test.skip=true package). There is classpath entry issue with
using jcalendar1.4 that is to be solved.
Added link in pom.xml corresponding to classpath issue. 
Added displayNoReportsFoundDialogue(...) method in DataEntryForm.java to
ask user confirmation for selecting new root directory. 
Main.java now uses displayNoReportsFoundDialogue(...) instead of
displayErrorMessage(...).
Added few constants.
DataEntryForm:
- Removed implementations of the ActionListener and Runnable interfaces (the actionPerformed and run methods), since these where not used.
- Updated the class Javadoc.
- Optimized imports.