Applying my tileset patch since nobody seems to have replied to bug 329

Applying my tileset patch since nobody seems to have replied to bug 329
- Tilesets are half the size
- attributes is now optional
- datas has been added to set data
- Multiple images can be specified
- Some error messages are now better
- Free tile list if(0) statement is added back
- if(0) tileset dump statement has been added
- Editor support should be easy (not included)

SVN-Revision: 5781