currentVersion, buildNumer and userDirectory

Hey,

I'm not understanding how bundle.properties and placeholder substitution 
is working. I believe the parameter values are coded in the source 
files.  How then can these values be over-ridden?

Of interest to me is my application's bundle.properties contains 
currentVersion = myappname {0} with {0} being replaced with 
netbeans.buildnumber. How is {0} resolved to netbeans.buildnumber?

Of greater interest is my applications userDirectory resolves to 
~/.myappname/dev/ whereas Netbeans 8.2 userDirectory resolves to 
~/.netbeans/8.2/

Where does "dev" come from and how can I replace these values?

-- Mark