Uploads .dae files

Upload .dae files rather than .kmz.
This makes the use of double_sided flag possible and uploading a correct model; sketchup takes the the parameter double_sided into account only when exporting .dae files but not for .kmz.
Thus it fixes the culling and z-fighting bug of faces by their own backfaces.

To group .dae and textures, the files are zipping using a command line tool.
For windows it was necessary to embed the binary 7za.exe.
For other OSes the zip command is used.