Allow openfire.bat to start in other folders

Currently the src/bin/openfire.bat file used to start Openfire will only work if the .bat file is run with the working directory set to the same folder as the bat file itself.

If this file could be run from anywhere, the sequence of commands 

mvn clean package
cd target\openfire\bin
openfire.bat
cd ..\..\..

becomes simply

mvn clean package && target\openfire\bin\openfire.bat