Addressed following TODOs:
//TODO: maybe it's better to put the responsibility for writing
properties in a separate Settings class? [Freek]  
//TODO: looks like updating the GUI is done elsewhere. If that's the
case, we can rename this method. [Freek]  

Created new class utils.PropertyFileWriter to delegate writing
properties to the property file.
MetricsParser.java:
Moved updateMetricsToDisplay(...) method to PropertyFileWriter.java
Renamed updateMetricsToDisplay(...) method to
updateMetricsSelection(...)
DataEntryForm.java now uses PropertyFileWriter to save dates selection
and root folder selection. 
ChoosemetricsForm.java now uses PropertyFileWriter to save metrics
selected by the user.