GPU installation broken

[tsampazk]

See #463.

Installing through git for GPU is currently broken. I have tested both master and develop in two separate machines, getting various errors.

Mainly detectron gives out this error:

RuntimeError:
      The detected CUDA version (11.2) mismatches the version that was used to compile
      PyTorch (11.6). Please make sure to use the same CUDA versions.
      ...
      ERROR: Failed building wheel for detectron2

I have CUDA 11.2 installed as suggested before.

Suggested temporary fix (by @Pavlos-Tosidis) is to remove the last line of GPU installation in install.sh relating to detectron, running install.sh and replace the [torch installation line] with:

python3 -m pip install torch==1.13.1+cu116 torchvision==0.14.1+cu116 torchaudio==0.13.1 --extra-index-url https://download.pytorch.org/whl/cu116

[tsampazk]

More detailed information on how to run a working installation can be found on #463