Packages can be placed anywhere.

This is the local continuation of #151

To recap, this changes how packages are scanned during start up.  A package must have the "package.xml" file, which must have a "name" setting to identify the package name.  If a package is found in the user data directory but not the game data directory or vice versa, the missing directory is computed from the found directory.

I've tested binaries for Linux (Debian 7) and WIndows (Cross compiled and tested under WINE).  Everything seems to function correctly with no breaking/compatibility changes with current file formats, so I plan on merging soon.