[horde] Transition to Composer

[Twilek]

Hi Ralf,

thanks for the detailed information. I hope that you succeed bringing  
Horde over to composer. If you have a reasonably working system I  
would gladly help testing things. My horde installation should be  
quite standard, althought it is very old (has been transfered from  
Horde 3 via Horde 4), so  I cannot guarantee 110% that I did not do  
some manual fiddling at some point in the past.

Regards

Henning