Add compression for gds generation

[skuep]

In order to use GDS3D with the remote filesystem structure over slow connections, compression (server-side) and decompression (client-side) would be nice.

For this, XZ compression should be used. The start scripts will have to be adapted in order to decompress the gds files, in case compression is used. In the skill script, compression should be available optionally.

[skuep]

In Commit 22b56b4, I have added compression support to the Skill script and start script for windows, since that is all I can test at this time.

I took the opprtunity and refined the generation of the launch scripts to a template based system. The templates are stored in a subdirectory and contain magic phrases wrapped in ?...? that are then filled within the skill script on execution. At this point in time, templates for MacOS and Linux are still missing.