* removed the forgotten material files of lake_ice
* unified tile descriptors in ufocrash.ump and rescue.ump

* to prepare converting the +ufocrash and +rescue tiles to templates
* unified size of Raptor dropship tile
* a first step towards sharing tiles over various maps

* started +shared (tile pool)
* moved all tiles from +ufocrash to +shared
* moved all tiles from +rescue to +shared
* +ufocrash and +rescue maps now inherit their tiles from +shared (+rescue was an extension of +ufocrash before)
* moving the tiles from +rescue was not necessary, but this way it is now possible for other maps to access the crashed Phalanx craft, too
* [+shared] replaced dropships by actual prefabs and rescaled ground texture
* map [+industrial] now uses the dropship templates as an exampel