CI: Use QT_QPA_PLATFORM=offscreen

WRG: silence warning 4275 : non-DLL-interface std::runtime_error used as base for DLL-interface Error

WRG: move gl::error implementation to the header so it is not exported in a dll in windows as std::runtime_error is not a dll interface (C4275)

ENH: new PantexTextureExtraction application built around the ScalarImageToPanTexTextureFilter filter

BUG: Don't try to open hdr file when looking for rpc tag because this makes the ENVI driver throw an error

BUG: in TrainImageBase do not connect sample.vnf to the cfield of the learning application because the input vectors are not the same