allow ./spring --game rapid://ba:stable --map DeltaSiegeDry

- split ParseSpringUri into dedicated file
- fix some bugs / cleanup / replace pointer with references

Note: idk if its compatible with all rapid clients arround,
tested only with springlobby/pr-downloader, it requires versions.gz to
be stored in <springdatadirs>/rapid/.somedir./versions.gz

see http://springrts.com/wiki/Rapid for more details about Rapid