More elevation models for Coreg-DEM-Refinement. [DemCoreg]

 Initially only SRTM3 was supported. Now all DEMs supported by NEST-core
 can be now parsed for the coregistration refinement, except for
 External DEMs.

 Additional parameter was introduced in the operator, and UI was
 polished to show DEM's only if refinement checkbox is ticked.
Update Coregistration Graph with new params. [DemCoreg]
Add 'tile extension' param for allow tuning of Topo removal. [TopoProd]

 Quick and dirty resolves #15