remove geometry definition requirement

[johntruckenbrodt]

Currently a user needs to define one or multiple geometries via config parameters aoi_tiles or aoi_geometry. Optimally this requirement is lifted so that a user can just process some scenes without knowing the IDs of the overlapping tiles or creating some geometry vector file.
The IDs of all tiles overlapping with a scene can of course directly be determined inside the processor. However, the processor is currently not able to determine whether all acquired scenes covering this particular tile exist locally. If this is not checked, an NRB tile with incomplete coverage could be created. See #8 for more discussion on this.

For the example scene below, only two tiles (green) can be processed without input from other SLCs acquired in the same data take (yellow):