CI setup now updates ci_env environment installed via docker_pyenvs instead of creating an independent environment.

CI Python environment is not separate from the base env. Fixed mixed channels for gdal and libgdal causing libkea issue during CI.

# Conflicts:
#	requirements_pip.txt
#	tests/CI_docker/context/py_tools_ds_ci.docker

Revised docker installer (now uses a basic conda environment and the gitlab runner container on top).